The snout (pilot) of the torque convertor fits into a recess in the crankshaft flange. This diameter is approx. 1.5" on early transmissions, and 1.8ish (working off memory here) on later convertors/flanges. This means the later convertors will not physically fit the early crank flanges. There is also a different input shaft spline count between the early and late 904s which prevents the early convertor from being used on the later trans. A custom convertor could be built, but for that kind of money I would seriously consider rebuilding your original transmission, and being able to avoid swapping columns and linkages and driveshafts... This is of course provided all those components are in good shape on your car (some replacements can be difficult to source). Sell your later trans to recoup some of the rebuilding cost, and you will have saved $$ on the other parts you won't need to change. Again, provided everything is in good shape. Just my opinion, and assuming you're keeping everything mostly stock. Good luck!​