Here's a couple of pics of my old mk3, rover v8,jag irs,and a nice chop,4 door converted to 2,
Sorry I could only find one !
Sold it about 30 years ago
Ford 289, 302, 351. A lot of South African cars such as Capri & Cortina were available from the factory with a V8. Do some research as some of the install parts will be compatible or maybe available or available from the aftermarket suppliers
Ideally a donor car will be afoot route, as you can get engine/box/axle. Although axle most likely will need modifying.
I would track down Steel City Cruisers and talk to them. Bound to be somebody there who can help and advise.
As for which engine, I guess it depends how deep your pockets are, what you can get your hands on, and how much you can do yourself.
Rovers are still fairly plentiful and they are light being aluminium block, although I think they are a bit longer than a small block ford or chevy.
Also worth thinking about where the sump wells and exhaust manifolds on the different engines are depending on if you want to rework or replace these.
there are some interesting modern alternatives as well.
If you look around on here you will find Lexus and BMW V8 transplants.
There is a bit more to do with wiring there though.
If it was mine, I would go small block ford, as Mopar_Mark suggested.