Quick question, can you use shocks from a late rearend to fit an early offest rearend?

No I don't believe so. I think they are different lengths. Just a guess, don't trust me until someone else says the same thing.

The length is different. Probably due to steel vs aluminum arma. Koni part numbers show one for 83-85.1 and another for 85.2-89.

You could physically do it, but it won't work right and will probably destroy the shocks.

As above, wait until an expert gives his opinion.