are they interchangeble?

I have a 1976 LTD 900 that I would like to replace the front forks from a 1980 LTD 1000, also I'd like to replace the front calipers with 78 Z1R calipers, so I can get rid of the hard line brake lines that are used on the 76 900 calipers & replace them with steel braided lines, will everything swap out with no problems ??

As long as you get the caliper brackets with the z1r calipers I think you should be alright,but Im not sure theres any advantage or difference between the z1r calipers and the stock calipers off the 1980 frontend if you have the complete frontend already.
You should also be able to get braided steel lines for the stock ltd calipers as long as you get lines with the right ends or find the right banjo bolts to work with them

Make sure you keep all the stock parts. Those bikes bring good money in stock configureation. You might sell it someday and it would make a big diffrence in price if it didn't have the original pieces on it.

Wireman, I dont have the complete 80 front end, just a spare set of forks that are in better shape than the 76 forks, and I also have a set of the 78 Z1R calipers that are in great shape, I'm pretty sure everything should switch over with no problem, just wanted to see if anybody had more insight than me

Roy, I do plan on keeping the stock parts I replace, but because there are already alot of non stock parts on it already, like paint job, kerker header, cal fab swingarm,chrome after market parts, I'm not going to worry about it too much, if it was completely stock, it would stay that way !!!