Transmission-change  Question

This question is for an old guy (not me) who needs to rebuild his 88 Syncro
transmission. He (and mostly his wife) has always wished his westy had an
automatic. He was asking me the other day if he could just drop his
driveshaft and have an automatic adapted to his 88 Syncro camper... I said I
didn't think so because of the gas tank's location and the under carriage
clearance.. Has anybody heard of this being easly done? He can get a donor
and will have the time and a barn to do it in over this winter.
I said just get a good used automatic westy and sell your syncro, but they
love it and he wants to know if someone has done it before. Like a lot of
old coots... he doesn't do this computer thing... so send answers to me and
I'll relay by phone to him.
Thanks.
RR