Something off of an 80 moto-bike would be cool but the problem is you'd end up with a chopper looking thing with the front suspension way out of balance from the rear. You could have someone make some spacers to install under the damper rods to shorten the forks which would require either finding some shorter springs or wacking them to size.
I initially set up my my CT-200 based bike with an XR-100 front end and a Passport swingarm w/13+" shocks to balance out the bike. It sits a little high for my munchkin legs, though so I bought a set of XR-80 forks (2" shorter) and will try it with those fork legs and either replace the 13" shocks with stock Passport units or install a CT-90 swingarm and use the shocks I have on it now which will basically give it a stock ride height.
With the XR-100 forks, Passport swingarm and 13" shocks it puts some daylight between the rear tire and fender which looks pretty cool. Angling the swingarm like that does funny things to chain adjustment just like what happened back when dirt bikes first started moving the shocks forward in the early '70's for more travel. I put an XR-100 chain slider on the swingarm to keep the chain from sawing a hole in the crossmember and with the limited travel of the shocks I'm hoping keeping the proper tension on the chain with that setup won't be a problem. We'll see.
Side note--to use XR-80/100 forks on the CT/Passport chassis you have to lengthen the steering stem. I sawed mine in two, turned a plug on the lathe to match the I. D. of the steering stem and had it heliarc'ed in place.