Everyone has seen the Vic 340 build by brett.
Question could you do the same with a G3 platform.
Could you do it with less?
Lets hear yah! Lol

Not with Less. The ONLY way your going to get max effort is to be able to get the maximum out of the cam & valvetrain. Pretty much the Gen 3 is maxed out at about .400ish lobe lift on the cam and .650ish lift at the valve. To increase that would require some considerable work and expense. The Cam in the G3 is pretty stout in size but it's limited in the amount of lobe lift used, unless you make the base circle smaller which defeats the purpose of that nice "baseball bat" of a cam and then that creates another issue with the lifter position in the lifter bores and the engagement and travel within the "dog bone" preventing lifter rotation. Or, you could go to a larger custom cam core with bigger journals, which would require the corresponding block work to fit it in. Then, to combat the Lifter travel issue, Keyway Lifters would be required to get rid of the need of the stock "dogbone" Lifter travel issue. Doesn't seem there's enough material in an Iron Block in the Lifter area for 1.06 dia. Bushings and .937 Keyway Lifters. Looking at a Hellcat Block in Cad, it gets pretty thin around the bore when enlarged to 1.06 dia, for the keyway bushing. I've seen they work in the Aluminum Blocks, but they appear to have more material in the lifter area. I would also use the Jesel Rocker Arm System to get more rocker ratio, as they offer larger ratios with that system. Then the next issue would be trying to getting enough valve length/guide clearance in the head for .900 + lift at the valve. With the stock length Valve, the guide would have to be cut down a ton to get enough Seal to Retainer Clearance for that type of Valve movement and then the guide would pretty short.

This is just my opinion based on my experience with these things and what I've done with my motor. Could it be done? For Sure! But, NOT EASILY OR CHEAP!! It's Going to take plenty of R & D, the Best Parts and plenty of money, like any Max Effort NA Deal for any motor.

I think the G3 is better suited for Power Adders to make max effort power than to do it NA. Easier to work within the designed architecture/limitations of the motor and probably less expensive in the long run.

What's the budget ?

@440 CI you need 2.3 Hp/CI to equal what Brett did with the Vic heads, @400 CI you need 2.5 Hp/CI
Apache heads will go over 400CFM with a 2.20X7MM valve and port work,but I think your better off trying with the ThiTek heads
I think Rockers are the only obstacle to over come(besides the cash to make it all work)
For lifters I'd use .937 keyway, or maybe .904 dog bone, (MY OPINION) your not going to achieve this goal with .842 DIA lifters,
it would have to have external oil pump.
6.1 block needs Darton sleeves to keep the cylinders tight at the bore size you need to make 1000HP NA. Bore needs to be 4.125-4.15 maybe 4.16.
BGE block ..from the sonic #s I've seen could mathematically go to 4.185. that would leave .120 as the thinnest wall , good thing there is it's never the thrust direction and it's usally cylinder no 8 at the end of the water jacket.
The added deck height of the BGE makes it the better Iron block candidate.
4.05 crank would max stroke even then your looking at a RR 1.53 with a 6.2 rod and a Pin height in the 1.04-1.05 range..
Steff's G3 is good one to look at as a starter, I think he made close to 800 at 400Ci (not 100% on that) need him or Ray (SIXPAKGUT) to step in and correct me.
Buddha boy's 449 Alum is almost 2 Hp/In I think he made 890HP @449 CI
HRH Performance has done 840/850HP @ 427CI with an Iron block and ThiTek heads...and according to them 6.1 lifters.
I KNOW a G3 can get close , I'd love to see what Brett could do with a set of Apache heads......is it Brett or Bret ?

Depending on weather, mine is more like 710-750hp, based on ET & MPH.

Why wouldn't 0.842 keyway lifters work? You would definitely need to have a custom one off valvetrain to accommodate any additional lift. Seems like even the new Jesel and T&D rocker arms are still limited to certain amount of lift. If you could get that figured out, I think that you may be able to make some things happen.

Who makes an .842 Keyway Lifter? The Jesel System that uses the cradle and individual Rockers has ratio options.

After doing a quick search, I may have been wrong. I really thought that I saw some used 0.842 Jesel lifters on Patterson/Elite Racing's web page but it looks like I was wrong as I'm not seeing anything in the web search I just attempted. Sorry for the misinformation.

Remember Bishoff's Engine Masters winning 401 G3 from a few years back .
they got a bit over .800 valve lift using 1.8 jessel rockers and SBC .842 lifters with the tie bar removed and modified dogbones . Not sure how reliable the dogbones would have been long term .

if you want to go modified Link bar lifter route it's actually simple,
attached is a photo of Jesel's Alum lifter yoke...it's not hard to duplicate...… best lifters to modify are Howard's Retro lifter part #91764
COMP Cams Retro-Fit Hydraulic Roller Lifters 8920-16 can be made to work also.
I have a 441CI (4.09X4.20) build running around the south east part of the country right now , pair of Philly boys in a 08 magnum hitting Street racing parts of the south with a set of Howards that are made solid. with a 6061 alum custom yokes....the stock plastic yokes once you cut them to modify them they are junk.

So is that Jesel yoke pictured, specifically designed to work with modified tie bar lifters.

No,that is Jesel's dogbone lifter setup for a GenIII.

I just posted the photo , so you can get an idea of how simple it would be to make your yoke,

.842s would be fine and are fine for 1.8 HP/CI builds, turbo and most blown set ups. but for a all out NA, the .842s would be a weak link for 2 reasons ,1) the largest wheel you can get in the .842s is a.750 DIA, the .750 wheel has a hard time dealing with the open spring pressure you would need , less surface area to spread out the load of the spring.
2nd reason is at this RPM 8K+ you need to hold the valve open as long as you can on the top of the lobe.....it's a similar to why all out flat tappet engines use .904-1.0 dia , look at the GM RO7/ROX and SB2 programs, Look at Australian pro-stock program, those engine are limited to 400CI and make can make over 1000HP, you won't find anything smaller than a .904 DIA roller lifter. so for a Max NA G3 we need to have a .800-.840 dia Roller, which you can only get in .904-.937s....+ it's easier to control the rate of closing with the larger wheel,
Steff pointed out that the 6.1 block and the BGE block(all Iron G3's) do not have enough room in the lifter bore to be enlarged enough to use a .937 Keyway with the bushing....I've used the .937 keyways with out, but It's not a street friendly idea....so that leaves us with the Modified link bar lifters....issue with those is there is not enough space between the heads and the block to use a link bar as is.I've used Comp cams LS short travel link bars in a 374 build, but the bottom of the heads(eagle)needed to be clearanced.
Answers are coming in the next year.

Now one of the benefits of the BGE and the 6.1 block is ….cam tunnel you can seal the cam tunnel off by taking a piece of Alum and attaching it to the oiler mounting boss.
Another advantage the G3 has is the nature of the crossflow head and the efficiently of the combustion chamber we should be able to hit 2.5 Hp per inch with less lift than a wedge or canted valve head...we just have to find that # and the RPMs

Thought you guys would like to see this. Started out as Jesel tie bar solid roller lifters off ebay for a Small block Chevy. Pulled the aluminum body out and made what I needed for the Hemi. They oil up through the pushrods and directly on the wheel. Re-used the pushrod cups out of the Jesel lifters. Going to use the stock yokes at first and see how it works out.

They look good, Necessity is the mother of HOT rodding,
Just be careful of MAX travel.