1977 KZdisc brake spoke rims on 1981KZ???

Hello, This is my first post so please forgive me for not introducing myself before. I live in SW Houston and have a 1982 KZ1000 J LTD, bought it from the original owner several years ago with only 12,000 miles on it. Family came along, and the project stalled.... Anyway I want to get this thing going, I'm not to crazy about the mag wheels, and I found a guy that has a drag bike chassis with a set of what look to be about 1977 disc brake hubs that have been laced into 18" Sun rims 1.85 front and 4.25 rear. He wants $550 for everything, rims look new, swingarm is a 30" long steel afair, and the chassis is junk.
The rear has a slick on it right now, but I think it should take a 150-160 size tire, which probably means a new swingarm. He has a LONG swingarm on the drag bike which I will get with the rims, just not sure if it can be modified enough to go back to near original wheelbase. Will these rims fit my bike drop in? Are there any simple mods that can be made to the stock swingarm to fit these rims with minimal change in the wheelbase?
Thanks,
Montie