With the following bolt ons what size fuel injectors should I run for the best results? 89 GT with Mac shorty headers and H-pipe, flowmaster 40 series style mufflers, underdrive pulleys, cold air kit, 75mm maf and throttle body, stock intake and heads, installing 3.55 frpp gears this weekend. The rest of the motor is stock with around 175,000 on it. I know its got alot of miles but doesnt burn oil or smoke and seems to pull good after about 2500 rpm. Any advice on other upgrades I should try are very welcome. Thanks. 

 keep the stock 19# ones as you dont need more fuel yet, however lose the large TB its not needed and is hurting your performance

You really don't need to step up to bigger injectors until you start Heavily modifying things like heads/cam etc.  even if you swap to a different intake the stockers will do fine. Just look to upgrade if you actually tear into the motor to change things up.

What size throttle body would you suggest for this set up? I noticed my take off was affected by the bigger throttle body, thats why I'm swapping out the gears as soon as possible. Thanks for the advice.

 I would keep the stocker on there, I have a 347 now with only a 70mm tb