is this a good idea to put my 1989 tbi 305 heads on my rebuilt 1989 350 and will i have to run prem gas and how much hp will i get vs the stock 350 heads and is that to much combustion

 

305 heads from 1985 are better but not much improvemant on a 350 check the want ad digest for some heads i just saw a set in there that wer 202 heads and thats what you want for like 400 bucks ......know if you wer going to take 350 heads and put them on a 305 that would be differant then you would have a rat 305 its a about the motor i also saw in the want ad digest a 327 block wth a th400 tranny for 900 bucks but you better beat be there lol

 

TBI heads are garbage. Whether they cam off of a 305 or a 350, they are trash.

Power lives in the heads. If your heads aren't adequate, then nothing else you do, can possibly overcome the limitations they put on the motor. No amount of cam, carb, intake, headers, or anything else (except nitrous or forced induction) can "compensate for" bad heads.

Get better heads.

There's no such thing as 202 heads. Chevrolet never used that casting number.

There IS such a thing however, heads that someone has installed 2.02" diameter intake valves into. That may or may not be meaningful. If the valve size wasn't the limitation to the heads' flow in the first place, as for example would be the case if they were TBI heads, then upping the valve size won't improve them.

Most stock heads aren't worth $400 no matter what size valves have been installed in them. Most of them in fact, putting larger valves in them is about like putting lipstick on a pig: doesn't change the basic fact of WHAT IT REALLY IS.

Buying a 327 won't improve a bunch of TBI heads, even if there's a Turbo 400 stuck to it. A 327 could have ABSOLUTELY ANY small block heads on it, from the worst to the best; they all fit, same as they would on a 283 or 305 or 350 or 400. Just being a 327 doesn't make any of that any more useful to somebody that already has a motor. And since the guy already has a 350, he doesn't have any use for a 327, even if it was free; it would be a downgrade.