366 Chevy Big Block

I've got a 366 ci in a 68 Chevy mud truck. This thing is pretty sound as is but was wondering what I could do to gain rpm. I want to put a cam in it and would like to know what duration I should look for. Thanks. Plz no this motor is junk comments, just want to know what I can do with what I got, thanks

It ain't junk, but it is the lowest form of engine to expect to gain much--

Small bore/stroke, long rod heavy 4 ring piston, small valves, low compression-----