new to mustang building.

Here are my plans as of yet. I want a respectable 450-500 very reliable and streetable HP. Plan on running a forged 306 with about 10 pounds of boost. G-force T-5. My question is what computer should I use. OEM , aftermarket, is OEM what year and part #. Thanks for the help.
 
I have to agree if 450-500HP is your goal, a large cube motor will get you there easier, possibly cheaper and can be very streetable. Personally Id go TKO600 over any G-Forced based T5.

To answer your question a OEM A9L which is stock in your car will be fine with a chip or aftermarket piggy back tuner.
 
Also agree with others...with a factory block, you'll be on borrowed time. The block could last a few years, or a few hours. Depends on how you treat it and tune it. I'd run a 351 based motor with a bit of boost and you're there!