'87 K20, has a 5.7L TBI and was converted to a 700r4 a while back.(was TH400) I used a prom from a 1/2 ton to handle the TCC lock-up... now he want's more power, so we are installing a 7.4L TBI. Is there a useable prom from GM, if not, who custom burns them?? ... Login to read more.