I bought a 1972 400 block and want to build it up with as many of the parts from my 350 as I can use. The car will be mostly street driven.
This is what I have planned.
AFR 195's w/68cc chambers
SRP forged flattop pistons 10.7:1cr
Scat 5.7" rods, either I or H beam
Scat forged 3.75" stroke crankshaft
Crane powermax hyd roller pn 119831 grind HR-284-2s-12 IG
adv dur 284/292 0.050 dur 222/230
Lift 0.543/0.563 with 1.6 rockers
112 deg lobe spread
Comp Cams pro magnum 1.6 roller rocker arms
Holley 750dp with proform main body
MSD street pro-billet dist w vac adv.
Jegs 2.5" dual exhaust
The compression ratio will be 10.7:1 and the dynamic compression ratio is 8.02:1, will I have problems running pump gas?

I have 2 sets of headers, hooker supercomp 1 3/4 and a set of Blackjack 1 5/8 full lenght headers, which set is better for the 400?

I also have a Edelbrock rpm intake and a weiand 7530 teamG, which of these intakes would wor best on the 400?

The engine will be giong in an 81 camaro with a munci m22 and 4.10 gears.

Everything but the pistons. I would use the small headers and dual plane. That's one screaming combo! I have a little higher DC and run pump 91 no problem.

Don't use a kickout pan if you run the Hookers!

Id use the 1.75" headers. I think that the 68cc chambers will make more than 10.7 to 1 in a 406..Better recheck that. The 74 cc may suit you better..
I think the manifolds might be a statistical tossup. Id run the Dual plane first.

Remember that 400's use an externally balanced flywheel and harmonic balancer unless you have the crank internally balanced.

I used Pat kelley's calculator for the cr and dcr numbers. I used 5cc for the pistons top and 4.155 bore, assumed the pistons were 0.015 below the deck, felpro gasket 0.041 thick 4.19 diameter,68 cc chambers.
cr 10.73
dcr 8.04
I am planning on cc'ing the heads to find out exactly what they are, those are the heads from my 350 with about 1,500 miles on them. I have looked at forged dished pistons, but they will lower the compression too much.

Sounds fairly similar to my 400. I put on 215cc canfields, Team G intake, 820 Demon, 10.75:1 CR, solid roller 285 adv, 242* @ .050, .600 lift on 106LDA. Runs pretty good.

The only suggestion I would make is to narrow that LDA, that pretty wide for a 400. 400's like 104-106, but 108 is OK too. You're losing alot of torque with 110 or 112. BUT, you gotta be able to cope with the idle!

What would be the better combo for my Camaro with an m22 and 4.10 gears, the first post or going with a bigger cam like this one
crane HR-296-2S-12 IG
adv dur 296/304 0.050dur 234/242
lift with 1.6 rockers 0.574/0.595
112 lobe spread
I was looking at cams with a 112 lobe spread so I could have a somewhat decent idle, and I already have a set of Crane hyd roller lifters.

Pistons .015 below deck + .041 gasket= too much clearance for good quench/squish. You're right on the edge.

Zero deck the block, install reverse dome pistons to drop the compression.

I've got no use for the Chinese crank and rods, but whatever...

i would run the 1 3/4" headers and the rpm intake and why not just run the 282s cam that's in your 350? it would be much cheaper.

When I disassembled the 350 I wasn't being careful and when I turned the engine over on the engine stand and all the lifters fell out all over the place.

I already have the Crane hyd roller lifters, the HR-284-2s-12 IG cam, and Clotes aluminum timing cover, I have the option of exchaging the cam and they won't charge me a re-stocking fee. I bought the cam 4 months ago when I was going to rebuild the 350, but I ened up not being able to use the 350 block and I ended up finding a 400.

tighten up the lsa on the cam, the piston speed on a 400 is faster than a 350 so it likes a little more overlap since the dwell time at tdc is less. Maybe a mild solid roller would work much better than the hydraulic roller.