Lol... big block engines...hehe
You've got a problem there Ragz: If you want real speed you're gonna need an engine that revs... in the .90 class that brings you to the ducted fan engines really fast...
You could also modify a stock .90 like the Rossi, but that's easier said than done, so you're better off buying an engine that is already tuned (meaning: a DF engine) in my opinion.
On the other hand, if you want an engine for a 3D type plane, you need something that is reliable, runs cool and has loads of bottom end power... exactly the things you won't find in a high revving engine...
So in my humble opinion you're going to have to make a choice between one of the two engine types, or just think long and hard, dig out the credit card and buy both engines
My choice would be the latter...