the 392 cam will not work in your block, what you want for cheap, easy, efeective is a 6.1 cam from an automatic car (manual trans cars did not have MDS), you can find them around $100 used on fleabay. Also if you can find em and afford em the 6.1 head gives you more flow and compression, I would not hesitate to take another .020 off them either. If you want to keep your 5.7 heads just shave em .030, these hemis are very friendly to high compression, I am currently running 12 to 1 in my daily driver.

I never could feel much performance difference from shorty headers, either get long tubes if you can find one CARB legal with the correct EO number or don't bother.

A little bigger throttle body will make it more throttle responsive and may give you just a hair more HP near redline. If you get a bored and ported factory throttle body it should go un noticed from an over zealous inspector as will a slight cam and compression upgrade.

Cat back exhaust might help a smidge, certainly can add some nice sound when combined with the little bigger 6.1 cam, same with a good cold air intake but again make sure it is CARB legal.