i dont want to do a whole lot to the engine i have, but im pondering having another engine built. 302 or 351?
Right so what you are really asking is how to make your car quicker?
Not how good the old 351 was compared to modern Chevy engines?
I'm only asking because they are very different questions and thusly require very different answers.
Going by your usename I assume you have a 95 GT with the 302ci engine.
In essence to get more power you need to get more air into the engine. This can be done by many ways:
1. Using what you have. Do all the bolt ons heads and cam and so on. And essentially maxmise what you can with what you have. This can be expensive and ultimatley limiting in total HP. While the 5.0 is a good engine it is not in the habbit of making 400rwhp easily n/a
2. Increase the displacement, either by using your exisiting short block or with a replacement unit. 331 is a common option and of course 351. The more cubes you have the more power you can acheive. But it is still limiting.
Assuming you can get say 80bhp/litre out of a 5.0 thats (80 x 5) 400bhp (flywheel). Now a larger engine built to the same standard will still produce the same specific output, so a 351 (or 5.7) would make (80 x 5.7) 456bhp (flywheel). There are other factors, and most people who spend the time going for a built block usually go for a larger displacement but because they are built they often acheive better bhp/litre ratio's.
3. Forced induction. This is always a good option and FI does rule when it comes to ultimate power. And often will not cost anymore than an n/a build or an engine swap.
Remember all n/a does is force more air into the engine, so it increases the effective displacement of the engine (i.e. a bigger engine
If it where me I'd just slap a blower on your current setup, along with supporting mods for a blower applicatoin (upgraded fuel system). This way you should see a massive increase in HP and performance. And just run it like this, if eventually you want more or you blow the motor up you can simply rebuild it, or swap in another. But this cost will be the same as just doing an n/a built engine now. So overall it won't cost any more to do it this way round.
Check out Kennebell, Vortech