Is it worth putting a cam in a 1990 5.0 motor with stock heads?  If anybody knows, how much performance can I gain from  it?  (using an E-303 cam)

"Car has 3.73 gears, bbk CAI, adj. fuel reg., MSD ign. 6AL, off-road H pipes, bbk underdrive alum. pullies, 75 shot of nitrous."  

An E-cam would be an excellent cam for your combo. Good street manners, and responsive power. With the stock heads and valves, a set of 1.7 roller rockers are the way to go, as well. Add a set of nice-flowing aluminum heads, and this combo will make really good power. Good luck.  

Thanks!!!

Regarding new heads, what is the largest flowing Edelbrock heads can I use with the stock pistons?  

If you don't want to change heads, the E cam by itself will give you a great performance gain. Combine that with new springs, pushrods, and rockers on your stock heads, and an aftermarket ignition.

For s street application you don't want to go too big on the heads. For a daily driver, you want the motor to make as much bottom end torque as possible.  

Getting the 1.7 roller rockers for the stock heads, would I need the Ped. mount or the stud mount???  

I recommend stud mount rockers, but pedestal mount will work, too.  

never heard of anyone putting stud mount rockers on stock heads, but I know you can machine pedestal mount heads to run stud mounted rockers. Maybe that's what Johnson meant? Just don't spend too much $$ on those stock heads. After market heads are pretty reasonable and usually a HUGE improvement over stockers.  

Does anybody know what is the largest intake/exaust valves that I can run with stock pistons on edelbrock heads?  In a year from now I will be building a 347, so If I can get a pair right now to work with the stock 302 and will still run great on the 347, then thats my goal before I take another trip to the track. "I don't want to have to buy two different sets of heads within a year."  I want the most power that I can get out of the 347  

I wouldn't go any bigger than 1.90/1.60 with inline heads and stock pistons. You can run 2.02/1.60 valves with twisted wedge heads though.

The best head on the 302 will be a compromise on the 347. Likewise, the best head for the 347 will be a compromise on the 302.