If its a roller capable block. Look and see in the lifter valley if there are bosses to hold a roller lifter spider or does the block have a cam retaining plate boss. Hopefully you have a 638 casting and it will be roller capable. Aftermarket tbi are not worth the money. There is no easy way to effiecently tune a obd1 computer. You would be better off going to a multi port, carb or leave it stock. I have wasted lots of money with name brand companys and achevied no more than before.
Call turbo city and discuss what you want to do. They are nice guys and if you are stuck on tbi, they can help you.