You've read various views here...even a suggestion to drop in a ZZ4 (which if funds are not limited is a good way to go), but I suspect, your project budget and the complexity of the task are key issues in this instance.
The L48 is a typical base engine with heads of limited flow, restrictive exhaust, mild cam that limits power at high rpm and a restrictive intake.
First, this disclaimer...my suggestions are given with the assumption that the engine is relatively low mileage (less than 50,000) and is in good condition, ie: no excessive oil use, no high cylinder leakage, no worn valve springs and etc.
If your goal is to do the best you can given the OE heads and camshaft, then adding headers, taking off the cat and going to true dual exhaust was a wise idea.
I'd also suggest an aftermarket intake because, even with the stock heads and camshaft, a manifold using current technology (40 years newer) makes sense because it removes the majority of any restriction upstream of the cyilnder heads. I'd suggest an Edelbrock Performer.
I'd have your stock Quadrajet properly jetted for use with lower restriction exhaust and intake. Finally, it's wise to recurve the distributor but....it needs to be done in a manner that limits centrifugal advance to work with an increase in initial. Often this means changing the distributor cam and ones with short slots are hard to find. I'd say, as long as you use 91-oct fuel, you need to start with 34-38° total adv. with 10-12 initial advance. Start with it all in by 3500 rpm then work down to get best performance without detonation. Once you have the centrifugal set, then add an adjustable vac. advance mechanism and limit vac. adv. to 8-10°
Have fun and good luck.
