well you could run 305 h.o head i believe but they would be quiet small and wouldnt breathe i would say pic some 350 heads up and have them milled and port and polished it will give u more compression and gett a good sized cam sense u will have the cu.inch

 

if you can get them to match up, dont run a cam with more than .430 valve lift. the valve would strike the piston with anything more, even with the dished piston. also, i believe the valves are smaller than stock 350 heads, which are 1.94 and 1.50. there is no way they can be machined to take 2.02 and 1.60 valves, i dont think they can even be machined to take the 1.94 and 1.50 valves. now you can get away with running a 350 head, but dont put a cam bigger than .500 lift in or it could hit the piston.

 

I just got two complete 3951509 still standard bore 400 sbc for $250.00 for pair.
I'm closing in on 50 yrs old, so street racing not my thing. when driving my 1986/87mustang with stock 1969 351W 4V with T-5 tranny and 3.27 gears. I very rarely go above 2500 rpms on the street or 4500 rpms on the highway. so I'm not wanting high rpm flowing heads.
my rebuilt 305 has heads# 14022601(305) heads on it. I would like to use those heads on one of these blocks for 87 black omen camaro. I not going to use the camaro for any thing but drive on the street and highway.
my question are;
1) what compression will I have with these heads on my 400 with the stock pistons?
2)will it run on pump gas?
3)would the 305 heads and 400 piston work with the stock replacement 327cid 300hp cam?

400 with 8.5 compression 175 hp/ 305 lbs =dog

I'm wanting 10 to 1 compression. so the I figure, the easiest way to get the compression up. is with the 305 heads.
every thing I put the 327 cam in, runs great for my kind of driving. so that way I plan to us that cam again.