Thanks for the input and is good information.

Cubic inches are your friend. The more you have, the less you have to push the valvetrain and rpm. If you can find a good 540 or 572 race motor and put a set of dished pistons in it and a mild roller cam, provided you have the budget, you could run a lot less rear gear and still meet your goal. That is what i am considering doing with my 528 when the day comes to retire from the track.
I would go 11.00 compression, 572 cubes, minimum head would be a 440-1 ported, dominater carb on a single plane intake, 2 1/8 headers, converter, tires and gears dependant on wheel well space. Biggest bias type slick you can run, gear it for 6500 rpm at 135 mph. Torqueflite with about 5,000 stall. This will allow pumpgas, and live a long happy life.
If budget dictates a stock block, i would go 400 block, 512 cubes, same top end, and high compression and run e85 to meet the goal easily. Use more rpm, but still be carefull on cam choice. You want something that will live a long time.

That is what "Tig" who posts on here ran at SPR I believe a few yrs ago, don't know all the exact spec but car weighs near 4000lbs, 11:1, indy intake, single Dom, .720 roller?, nothing too wild, -1's, 10.5x29.5" tyre with 4.10 gear, don't know about the stall, he ran 9.6's with a best of high 9.5's I think, that motor was making some power 870+ to run 140mph

Realistically, in a 68 Charger, he is not going to lose 1200 pounds. He may be able to get it down to 3400 pounds if he is really conservative, removes heater core, all AC components, back seat, exhaust system.
I ran a 68 Coronet w a Hemi and that is what we had to do to get it down to the minimum weight in SS years ago.
SO figure a car weighing 3400 pounds whim int. How much power does he need to make to get the times he wants?
Build a solid lower end and add a power booster, either turbo's or spray it with a 200 shot.

Turbo is the cheapest route.

It’s a stock block with billet mains and lifter bushings.
If I had a do over I would for sure find an aftermarket block for this type of power.

My old pump gas Duster weighed 3450 Lbs. with me in it, that motor made 727 HP in Klamath Falls,OR at 4300 Ft. elevation, it would run low tens in Vegas in the spring, best ever was 9.993 at 134.7 MPH at Woodburn ,OR(track elevation is 180 Ft. above sea level) in the late summer That was using 91 octane Oregon pump swill with the air cleaner and full length three inch exhaust on using a set of M/T 10.5x33x15w four year old drag slicks, it ran a bunch of 10.000 ET with the old type 315x60x15 M/T ET street radials on it
No trick parts in that motor, trans or drivetrain other than a coil over ladder bar rear suspension
My main message is that the whole car needs to have decent parts in it from the front to the back to go fast all the time

I've run it as high as 23psi. That's about all the fuel system is good for... the turbo has more left, but the single needle carb and A1000 fuel pump are about at their limits. Custom Diamond pistons at 9.2:1 compression ratio. Ported Edelbrock RPM heads. Cam is 232@.050" with around .540" lift.

Its a pretty basic low RPM combo. The boost does all the work... Shift light is set to 6,000rpm.

It's all relative... if you keep the timing safe then it doesn't have a ton of cylinder pressure. Keeps out of detonation, and the motor doesn't turn much RPM. I do run a diaper on it, but it's been together for 5 years now and gets beat on fairly regularly. Even last year when I was going through school (masters) in the summer, my best friend ran the car around all summer. He was driving to work 25 miles each way at least once a week.

Honestly I ran it for the first time in September of 2012 and it went 10.99 the first night out. By May of 2013 in it was in the 10.60's, and by September of 2013 it was in the 10.0's So not too bad. I would say I fought traction worse then power. When it started it only had stock springs, 2.76 gear rancho shocks, and 255/60 drag radials.

When it went 10.08@136mph, that was with a 224@.050" cam, home ported iron heads, 3.23 gear. Honestly its so easy to make power with the turbo stuff, it's really just having a good chassis to put it down as much as anything. But once you get it figured out, it's great because you can dial the power back on the launch with ease.

I agree with this approach (572) it will take plenty of torque and hp to move a 68 in Vegas air ! High density altitude is brings alot of frowns to racers faces ! It took close to 700 hp to run 9.80 in my Duster (3000 lbs) in 4800 ft air in a reasonably well sorted out combination.

I also like the idea of Gen 3 hemi with a supercharger as well.

I have a 68 Dodge Charger that will have similar goals to yours in the future...just got to finish the Duster first.

The boost does all the work
This^^^
If the turbo is selected well (like, ask the manufacturer?), the rest doesn't matter nearly as much as NA.
If it's not (2 common mistakes: way too big (88mm on a 318), 2.0 A/R (no boost below 6,000) the rest is a waste of time.
The difference between a tuned header fabricated to fit and a pair of iron logs may be 50 hp on a 7-800 hp engine, and $2,000. A bad cam choice (typically too narrow LSA) is worse than the stock cam.

But you don't get to say "It's 800 cubes".

What cubic inch RB, Hemi or Low Deck? 499 RB
What brand block and what was prepped? Was block filled? factory RB block
What cylinder heads,who ported them to what CFM and CC chamber volume? Indy SR. MW ports. cut to 68 cc
Rocker arms,ratio and springs? Indy 1.5 . flat tappet cam 608/615 280/284 ( i think. i dont have the cam card in front of me )
Intake,carb,spacer? Modman with 2 edelbrock 750s
What headers? TTI step
Compression ratio using what pistons? 13 to 1 wiseco flat top
What stroke of crank and rods and brand? 4.15 eagle
Oiling system? Fuel system? external with milodon pump. fuel is all aeromotive
Transmission are you running? 727 with good drum and all good parts. ATI 8 inch 5000
What rear gear? Type of differential and axles? Moser 60 with 4.10 gear

What is your ET and MPH went 9.863 @134.07 this weekend at 3600lbs

match the parts. match the combo

What range of DA readings does Vegas see?

From bad to REALLY bad..............

3300 Ft in the winter and 7700+ in the summers at night

Ugh...

Some of my local Mid-Atlantic tracks are comparable to Woodburn, so I'm sure there can be a pretty big loss of performance going between those two tracks.

Good plan on the diaper. Impressive combination!

My pump gas Duster with no changes from Woodburn to Las Vegas lost two to three tenths ET and 2 to 3 MPH in the spring, my old race Duster would change .4 ET and between 3 and 4 MPH from winter to summer up there with no tuning
BTW, in late July and August it gets worst when the thunder storms are brewing

Good to know.
Im aiming at 9.80's, my 3750#, 528, 95% street car has been 10.1 @ 134 but I want those 9's bad. Been told I have around 20% convertor slip so getting that sortedand rebuilt to 5000 plus some new shocks.