when looked under the back its got an independent rear end with coils + a transverse leaf spring.
when did the first independent r/end isuzu come out?

Bellett was first....

That is news, i wonder if isuzu built the dato 1600 rear end for datsun.
Even though this car is rusted beyond repair and the missus didn't want another wreck around the house the whole family really loves this car.
I may end up getting 2 door eventually.heard of a guy having a 161 holden motor in a bellet.Got me thinking about a 265 hemi conversion.

GT is the 2 door. Start saving $$$.....
Isuzu had nothing to do with Datsun's version.
Without major surgery, a Holden 6 (or anything else) will never fit. A Bellett engine bay is smaller than it looks. The "161" you may have heard of could be a G161 Gemini 1.6 which still is a project to fit.

2 doors are that expensive? how strong are the diffs. how much hp would be too much for a bellet diff?
did isuzu model the bellet off a hillman or vauxhall?

Good GT: $20k.
Diffs will cop plenty. Well known rotary turbo race car around here had 340hp and 10" slicks and it didn't break. Axle bolts are the weak link.
I've busted a diff, and bolts, unis, etc, in my race car, but the diff was because I was brutal. Not the diffs fault.
Bellett (with 2 T's) is Isuzu's design. Some Hillman influences but that's it. Vauxhall had nothing to do with Isuzu (nor did any GM product) before 1974.