Mike,
Transmission jack sounds better option Mike. You can tilt them if needed, when refitting through a twin plate clutch you do not want to be pushing and shoving as it is easy to damage a clutch plate, then you get drag :shake:.
I used to use on on the 15 speed Fuller Roadrangers, made life easy.
Recollect setting up a gantry in the cab of a Martian gun tractor once, to change a transfer box.