That's a nice ride you have there. That 400 sounds like it will need a valve job soon. Or maybe something more expensive. I know it is hard to wait a bit. But the best course of action is to save enough cash up to do a proper build on a good 400-455 pontiac core.
I myself am doing a solid roller cam 428. And believe me it takes time to do it right. If you rush and blow up the motor you will be banging you head against the wall.
And because your car is so nice. You might want to put a kill switch on it. Especially being SoCal and all.