Well, I know your going to have to replace the bell housing. Someone else will jump in here soon and tell ya everything else though.
There are so many toploader variations that its difficult to say if it will bolt right in. Many toploaders will in fact bolt right in using a 3 speed Maverick crossmember. The worst part about your 390 version is that you will have to change the input shaft or it may break. The 390 input is shorter than the small block versions so less of the shaft is supported by the pilot bearing/bushing.
The 390 input shaft is only part of the problem... The worst part is that Torino toploaders are longer than the Mustang version needed for a Maverick install. The Stang units were made with C4 dimensions and parts compatibility in mind, while the Torinos and larger cars were made with C6 parts in mind. In other words, a short tail toploader (Stang), uses the crossmember, driveshaft, mount, and shifter location of a C4. The long tail (Torino) version uses a C6 crossmember, mount, driveshaft, etc... None of which were ever made for a Maverick. Dave
