Proton Jumbuck - Engine swap and RWD?

Hi guys,
Need a couple of suggestions for my latest predicament...

I have gotten myself a Proton Jumbuck, it was a cheap project canvas really as the head gasket has gone (several times as i understand it) so the engine is coput... no worries because I never planed on leaving it in anyway.

First question with an engine mounted Longitudinaly will a straight six fit in or is that a job requiring a 3-way for a grinder, welder and the bulkhead? I havn't actually looked yet as the standard motor is still in..

Second question and this is the killer what options for a rear axle with diff are there besides the mitsubishi Libero GT because they are only a legend now..

Any help would be amazingly useful, if it helps i'm no stranger to the arts of custom fabrication I just prefer to avoid it when I can.

Thanks in advance