Hi everyone!

I'm about to buy my first small block car, with a 350 inch engine

The owner told me it "only" is around a 145 hp engine.

First of all, how do i check that?
And i know there is a lot of different 350 engine, all with different output.
So, whats the difference on those engine? The heads? Valves, exhaust etc.?

If i want to remove the "limits" (get more HP) where should i start?
Would a new exhaust (3") and new manifold do the job? Or do i need, valves camshaft etc. to get more power?

Thanks in advance