Just bout this 280 and am currently working on giving her an overall tune-up. I have the dreaded "rear-end clunk" i know i need a mount but i cant find one anywhere.. any help?

Try the dealer, msa, black dragon, courtesy nissan?

The 280zx does'nt have a diff mount as such. It is bolted thro the crossmember and has 3 insulators, 1 on the diff cover plate and 1 on each end of the crossmember.