For best performance you should look into straight thru mufflers like
Magnaflow, Dynomax, Jones, etc. If you can't drop your keys through the muffler then it's not the best performing muffler. I will be switching soon myself. As far as heads go the 190's will work fine but you won't see much of a difference in performance for two reasons, 1) you will be choking out the heads with the GT40 intake regardless of porting, 2) You'll be reaching the limits of the stock block so you won't be able to take full advantage of the larger heads. The 190's will have better resale value in the long run and a lot of people are now going toward big head small cube builds. To make that type of build successful you really need a custom cam and be sure to have larger headers. Intake and exhaust velocity is critical and having too small of headers can hurt performance a lot. There is a great thread on Corral about this and a lot of good advice given from Ed Curtis and Buddy Rawls about why the cam makes or breaks this type of combo.
47lb injectors will be too small for a HCI 302 with boost. You'll need about 60# per/hr injectors.
Inj Flow Rate (@ 40 psid) Naturally Aspirated hp (@ 0.50) Forced-Induction hp (@ 0.65)
19 lb/hr 258 hp @ 85% Duty Cycle 199 hp @ 85% Duty Cycle
24 lb/hr 326 hp @ 85% Duty Cycle 251 hp @ 85% Duty Cycle
30 lb/hr 408 hp @ 85% Duty Cycle 314 hp @ 85% Duty Cycle
32 lb/hr 435 hp @ 85% Duty Cycle 335 hp @ 85% Duty Cycle
34 lb/hr 462 hp @ 85% Duty Cycle 356 hp @ 85% Duty Cycle
36 lb/hr 490 hp @ 85% Duty Cycle 377 hp @ 85% Duty Cycle
38 lb/hr 516 hp @ 85% Duty Cycle 398 hp @ 85% Duty Cycle
39 lb/hr 530 hp @ 85% Duty Cycle 408 hp @ 85% Duty Cycle
42 lb/hr 571 hp @ 85% Duty Cycle 439 hp @ 85% Duty Cycle
44 lb/hr 598 hp @ 85% Duty Cycle 460 hp @ 85% Duty Cycle
47 lb/hr 639 hp @ 85% Duty Cycle 492 hp @ 85% Duty Cycle
60 lb/hr 816 hp @ 85% Duty Cycle 628 hp @ 85% Duty Cycle