chevy heads

I have a set of 896's and 416's and the casting is 261 how do i get the most horse power and performance out of the engine.
What's the most I can get out of the engine with these heads?

I do want to use the 896 but I'd rather not pay for the machine work to be done.Does anyone have any Ideas on this? I was told that it would need new valve seats and valve guides to burn unleaded gas.

http://www.corvettefaq.com/c3/Standa...ng%20Guide.htm
try this link I hope it helps, it got me about 20 h.p. for under 100.$ . use the old heads, they flow better. hope it works since i never tried to send a link before. mike