a good motor that a lot of people forget about is the old 283 corvette motors... they're a very good high RPM motor with a short stroke.... it'll kind of remind you of the 4cyls you're used to but instead be a v8.... they're a good quick motor and lighter weight than a 350..... the availability on them is a little less though so it would be something you'll have to do some looking for..... i've had a coupla 283s and i loved them.... they're great for road racing and the such.... i used to dump mine at 6000rpms and just launch in my little nova....