80's A998/A999 into Early A

If it's an overdrive, it ain't a 904. It's an A500 or A518 and will require major modification to the floorpan and crossmember. Probably what you have is an A998 or A999 lockup style 904. That WILL bolt right in requiring the yoke change and the shifter linkage change you mention. Also too make sure you get the kickdown linkage right. The hub register on the crank is also different where the converter hub rides. There is an adapter ring you can get to solve this. It's cheap. I think CharlieS and slantsixdan both offer it, or can tell you what to get and where. I am not familiar with it enough to know, but they are. It's an easy swap to do and the lockup converter will help you get some better mileage on the highway.