We have a 1989 Corvette that the gear was changed in the rear end. The original gear set was 355, the new gear set is 256. Now the speedometer is off. I have heard a few different solutions to my problem. One is a new Prom for the ECM. Another is either a brac module or a drab module. I have not been able to find any of these things anywhere. It is an digital speedometer. Can anyone help me?