IMO, if the stock heads are in decent shape use them, If you don't have alot of money to work with, don't get caught up in all the "YOU NEED" this & that, A simple stock 400 will have enough torque to keep you happy, I'm talking stock right down to the rotating assemble, That little xe256 you have will work just fine in a stock 400, If you want, just add bolt-ons like a decent set of headers (1.5/8) & Perf. intake, I got caught up in the "your compressions too low", The stock heads are junk, your leaving too much HP on the table Yada Yada Yada......, I'm "somewhat happy" with my 406, its got Iron eagle heads, decent cam, 10.4 compression, 750dp, RPM intake, headers, but i had a stock "re-ringed" 400 in a 78 2wd blazer back about 12 yrs. ago, all it had was headers & RV cam, That Blazer was a blast to drive, loads of torque, & yes, it had the crappy 882 heads & 8.1 compression, that was it, nothing fancy.