I'm pretty sure you CAN swap the R151 tail onto an R154....But like you said, if you have an R151 to swap from, why would you bother?....Unless your're trying to run an R-series trans behind a Supra motor....

As to the input shaft, according to Marlin, THEEEE Master, the input and gear ARE machined from one piece... <img src="/forums/images/graemlins/frown.gif" alt="" />