'82 650 Maxim to '83 750 Maxim Forks (Dual Rotor Swap)

Hi, first time posting on here so I apologize if I've forgotten something or posted incorrectly or anything like that. Anyways, I found a great deal and picked up an '83 750 Midnight Maxim to use the forks and brakes for the dual rotor swap on my '82 650 Maxim. My 650 now has 5k miles and is in beautiful cosmetic condition whereas the 750... is not. Anyways I knew that '83 was the year to get because of the brake (union?) piece is the same between the to and whatnot. My question is, since the forks are the same diameter and possibly (probably?) the same oil capacity, are the two identical enough that I can use everything off of my 650 and only use the lower/outer tube from the 750? The upper/inner tube from my 650 is pristine, all of the springs and internal parts have those same low miles, and since I didn't plan on doing the swap so soon, I've also just rebuilt the 650 forks about 1k miles ago. I'd like to retain as much as possible from the 650 and believe I should be able to but wanted to know if there was any more insight to be given on this. Thanks in advance!