We’ve recently discussed this very issue in another thread in this forum, and I learned something new in the process: Where an ICE gets peak performance at a relatively low rate of RPM, an electric motor tends to be most efficient at a high rate of RPM.
So, mating a replacement electric motor to a transmission that is designed for an ICE would not work well, because the electric motor would continuously function in its least efficient RPM range, particularly if the transmission is an automatic, but also with a manual transmission, in which the lower gears are not low enough.
Here is a link to that discussion: For the luddites in modern time