To run the 7427 there's a few changes that I know you'll have to make. The trans change is you can simply remove the early force motor and install the 94+ style. This will work, but you will have lazy line pressure changes since the accumulator for the force motor will still be in play. You can remove your valve body and use a BB or check ball to block the force motor accumulator to make the line pressure respond quicker, or just run it as is, and it will respond like any other 91-93 4l80e. You will also want to replace/update your internal and external harness if you haven't already done so. And if you have a 4x4, you will have to install a VSSB instead of your current DRAC. The VSSB has a conditioned VSS output that gets sent to the ECM whereas your 91 had the VSS going straight to the ECM. I've heard you can change the flag for the VSS in the programming for the 7427, but VSSB's are cheap, so I would just stay with the OEM set-up to avoid any quirks.