[Moppie]

Well there are guys down here who get over 300hp out of them useing a 4 barrel Holly, some headers and a wild cam.

Apprently theres a cheap adaptor plate for the intake manifold thats makes it a very easy conversion.

The other option for real hp gains would have to be a S/C.

But certinaly doing a good custom exhaust is a great place to start, and then work on the intake side.
Any good exhaust shop should be able to build you a suitable system.