1. Mounts will be custom.
2. The custom bellhousings are from Castlemaine Rod Shop in Australia. Due to gearbox length differences, it is almost certain that you will need to change the drive shaft. I can't remember what the output of an R154 looks like. If it is different to the old W58 gearbox then you will need a yoke on the front of the drive shaft to match.
3. The 1UZ-FE was always automatic. See Castlemaine Rod Shop.
www.rodshop.com.au/newprod3.htm
4. The alloy 1UZ-FE weighs similar to the old cast iron 22R. Just get some RA65 springs and dampers that suit your driving style (usually lower and stiff but that's your call).
5. The T series diff in the ST or GT will not survive but the F series diff in your RA65 convertible will be happy.
6. Mick's '77 Celica with 1UZ-FE is good.
http://members.iinet.net.au/~stepho/mick.htm
My currently stalled project for a 1980 Carina 1UZ-FE is here.
http://members.iinet.net.au/~stepho/mods.htm#CarinaV8
- Stepho