I have a 1970 c10 w/ a 350, what's the best and biggest camshaft I can put in it for more power?

IMO Big camshafts normally cause the engine to lope and run rich because they don't start making full power until high rpms. You'd have to rev up the engine high if you were going to launch at a half decent rate. If you have an automatic, then you'd need a high stall torque converter and some kind of shift kit in the trans if you expected to move quickly from a standstill. With a more moderate high torque range camshaft you can get good power and decent idle... With my one ton dually I had a mild cam and a shift kit and I could boil the dually tires any time I wanted. Course there's not a whole lot of weight in the back of a truck.

Try the 300 hp 327 cam. I like it in my 1969 gmc 350.