injector size

The 19s will be fine but if you're worried 24s will work also.

I ran the stock 19 lbers on my 93 which had TFS stage 1 cam, GT40P heads, TFS trackheat intake, 70mm TB, 76mm MAF and full exhaust with no probs. I would be comfortable with the stock injectors provided they are in good working order but if you are not comfortable with them you could step upto the 24s

go with the 19s and you'll be fine.

you can go with either, you just need to have a Mass Air meter calibrated for them.

if you just slap 24's in a motor with a 19# MAF, it will run like crap.

19 lb injectors/.5 = 38 - 38 x 8 = 304 HP
24 lb injectors/.5 = 48 - 48 x 8 = 384 HP
30 lb injectors/.5 = 60 - 60 x 8 = 480 HP
36 lb injectors/.5 = 72 - 72 x 8 = 576 HP
42 lb injectors/.5 = 84 - 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

304 HP x .85 = 258 HP for 19lb injectors
385 HP x .85 = 326 HP for 24lb injectors
480 HP x .85 = 408 HP for 30lb injectors
576 HP x .85 = 490 HP for 36lb injectors
672 HP x .85 = 571 HP for 42lb injectors

You'll be fine with 19's if you increase fuel pressure, or if he has the money just put in the 24's with a matching MAF. That is if your/his budget allows.