I'm parting out a 1983 NU50. Here a link to a Dropbox folder full of part pix.https://www.dropbox.com/sh/tsmmfgfzjo2k9z0/AACCbuc2JsvTQ1nBmcRRsD11a?dl=0
I've got one off an '83. Great shape on outside but a mouse gnawed a little on the inside. photos here:https://www.dropbox.com/sh/izyurjgaddf503j/AAA7-t2O3NurXZcvxxKSwSara?dl=0
I've got an NU50 cylinder, but I'm pretty sure you'd have to have it bored for the next size piston. I can get it bored for you--there's a machine shop next door to my shop. I'd sell the cylinder for $15, boring and honing for the next size piston is about $65 I think. Shipping depends upon where you live; I'm in Kansas.