NOTE; Application to base answers on, is a 1983 D 250 3/4 ton truck, 2 wheel drive 318, 727 trans, 3.55 gears, 235/85/16 tires (32" tall/narrow) stock original 25 year old shortblock incl the cam. (2 barrel motor) and NO, a cam change is not in the plans. Daily driver, not often used as a "truck" but when it is used as such, it is probably over worked. (<10% of the time) 119K miles (verified not 200K+) as it was a 1-owner before it was mine

(1) Rather than to send the Magnum heads in to be drilled for an LA intake can the LA (either OE, or aftermarket versions) intake be modified to work on the Magnum heads?

(2) Yes, I know that the Magnums have no center port from which the EGR can feed (Yeah I know they carboned up anyway, on the LA series) but aside from that, I know an LA engine EGR could not be made to work, (92-95 it was off the back of the intake via a tube that went to the ex manifold, 96+ engines did not even HAVE EGR)
BUT; if your '80s 318 passed with the stock heads would it pass sniffer with the Magnum heads (assuming same carb and cam as it passed with the LA heads) ; I know a visual would be tough w/o the EGR at least "appearing" to be hooked up and functional); this is kind of a "devils Advocate" Q, as I don't have testing where I am at. If I was not gonna be swapping these heads I'd be blocking off the EGR anyway. Like I said; Devil's Advocate question here.

(3); which aftermarket, made-for-Magnum heads intake, would be better; I know MP sells a single plane 4 bbl intake; but for my purposes, I am only considering dual plane manifolds.
My choices are the Edelbrock Air Gap or the MP Dual Plane? Would the Air Gap prevent percolation problems on a hot motor? (Had that problem with an AFB on my old Diplomat that I put headers and 2-1/2" true catless duals on.)This Truck has factory 3 row, Maximum Cooling package radiator. Any other advantages/disadvantages to either of these intakes?

(4) which bypass hose and upper rad hose; LA or magnum (still has LA water pump, timing cover and accessories)

(5) any issues with either of these intake manifolds, keeping the A/C? (personally I don't care, but my wife has asthma; A/C is handy in the summer) also partly why I am asking above, about modding an LA intake to fit the Mag heads, though. Because I know the AC works with that setup.

(6) How much difference in CR, between using the MP 0.028" Magnum head gaskets vs a stock set of LA engine FelPro's (~0.042" if I remember correctly) more than a couple tenths of a point?
(6a) what CR can I expect compared to the stock heads? (I don't wanna have to run Premium)and I have both sets of head gaskets here.

I have a set of fresh Magnum heads sitting here collecting dust; the valve guide seals on the original heads are shot (25 years old; SURPRISE, huh?)
Also I am 98% sure I am using a 625 CFM AFB. (just won one via Ebay incl a Strip Kit)
and the LA intake useability question also has to do with having an Edelbrock LA series Performer intake here already; I had a brain fart and was briefly thinking of putting either the stock 2 BBL on it or even a 2 BBL version of an SP-2P that I know of I can get; any of these would be cheaper than buying either an MP or Eddy Magnum intake (disability pay sucks) and I DO NOT want the Crosswind; I refuse to put a Made in China intake on my truck!
Already have the pushrod and lifters covered, too.
Oh yeah; (7) Do I have a choice whether I use the LA or Magnum ex manifolds? (can't afford duals right now so have to use whatever works with teh stock exhaust for the time being)

A member here used to have a jig that he rented out or let people borrow to redrill magnum heads for LA intakes. I'm not sure if he still has it though. Maybe someone can give an update on that. Good luck

I know that Hughes also drills Magnum heads for LA intakes; is that to say, that drilling and re tapping a set of heads would be a better alternative than modding an intake?

I think you will have a lot more intake choices if you redrill the heads. You already have a Performer, which would be a good choice for what you want to do with your truck.Plus, all your AC stuff should bolt right back to the Performer. Maybe check to see if a local machine shop could do it by using an intake gasket as a template.

(1) you can redrill a LA intake & use slanted spacers (3) An air gap would run a bit cooler but the main problem is the high volatility of todays gasoline (4) I dont know (5) I dont know (6) my magnums(uncut) are 63 & if you know your actual deck height you can go here a very user friendly user site & plug it in to get your actual CR http://kb-silvolite.com/calc.php? If you can achieve .035-.040 quench (piston to head) that will contribute more to you being able to use a lower grade of gas with out pinging than just the actual CR itself. (7) Same. The "jig" has been retired & sold

magnum heads are 63CCs? I have never had a set CC'd but all the printed literature I've seen, says they are 59-60 cc. except (1) set of MP ones which according to their catalog is only like 53 CC. How do these numbers compare to a set of '163 318 LA heads? (that's what's on the engine now) I mean common printed numbers; I know that I won't know exactly what "this" set reads w/o CC ing them.
On the quench, unless my pistons are heavily coated w/carbon (possible because of the oil usage thru the guides) this is a dead stock shortblock and I do not have it apart yet but we all know that by the 80s (my truck's an 83) Mopar was not into zero-decking their pistons, don't we? so even with the thinner head gaskets I have bought I doubt I'll have less quench than you specify.

Also are these slanted spacers available somewhere, or are they something I'd need to make (or have made by a local machine shop?)

Oh and thanks for the help so far guys. I am planning on having all I need for this head swap by the time my wife has her elbow surgery done, so I can have a "chase vehicle" here to run for parts with, so I have most of the month to figure out what I'm doing with this, manifold wise. I'm leaning towards one of Hughes' Edelbrocks he advertised on here a while back. but would loke to experiment wit different ideas while it's apart for future reference.

I have made my own jig and used it several times very sucessfully.

You should use an LA head to build it on to get proper angles and heights.

First I bent a flat 1/4 inch thick flat stock steel to go around the deck surface around to the intake surface and drilled a hole through it a little bigger than the intake bolt hole and in the aproximate location of the bolt hole. Then I took a tube about 3 inches long with a 11/32 center hole and took a long bolt about 4 inches long and bolted it all to the LA head and welded the tube to the flat stock that was bent around the head and took it off and there was my jig. You have to make it on the center intake bolt holes on the LA head and when you drill the end bolt holes on the magnum head you have to use a 19/64 spacer on the head deck surface because the LA bolt holes are not on the same plane. I just use welding clamps to hold it on the magnum head and move it for each bolt hole.

Also about the CCs most I have seen are 62-63 CCs. Chrysler was notorius for makeing chambers bigger than what they published.

The only magnum heads I have seen in the low 50s are the Mopar performance aluminum magnums, the pair I have for sale are 53 CCs.

if you're buying new magnum heads instead of getting some from a junkyard, the enginequest 318B's use an LA bolt pattern.

Thanks Patrick; but I already have a few sets of stock Magnum heads around, incl 1 set that was from a 380 HP Mopar crate (NO they are not for sale; that set is spoken for!)

I just got (2) Holley Economaster 4 barrel carbs that I may experiment with, once this change over is done.