i need to updated my former 2 cents
an isuzu rearend is a front loader rearend like the toyota unit plus you have a good variety of stock gear ratios 3.44 3.73 4.10
some came factory with LSDs some not but these would be the 4x4 ones they are very close to the correct size, they came behind v6s and they are a gm unit

they have a good aftermarket like the toyota but not as cheap
but heres the thing i find the best
the trooper units all came with rear disc brakes which i think is a plus
this is what my swap is consisting of
the trooper unit with rear discs
single piece drive shaft
and a truck arm style suspension like in winston cup nascar
it eliminates the torque tube/arm approach and is the best setup for both drag racing and road coarse and it also makes a leaf spring axle an easy swap because it uses the leaf spring pads to attach to,which are at the same spot on the opel axle
for more info look at
www.hotrodstohell.net they will make a custom setup so it will be easy
i also think it is a much cleaner setup
as soon as i have more funding i will be doing this so i will keep you posted on my own thread