It's great to see some upgrade parts are already out there for this trans. I have rebuilt 727's in the past and I really like the idea of using a modern overdrive in an older body. If you plan to use a mechanical speedo, you will need to use the modified tailhousing. If you plan to retain your stock dash and instruments, you are pretty much comited. I used the electronic Dodge truck dash so I needed a VSS signal and convertor. There are lots of aftermarket electronic gauges out there. One added feature of my setup is that I can use a plug in scanner and performance tuner in the OBD II jack.