I've got a 62 Redface that I'm restoring to. I just battled the knobs about a week ago. What I did is I went to Napa and got this stuff called PB blaster it is some awsome pentrating oil. I sprayed alot of this stuff on the knob where the shaft goes into it and the set screw let it soak a while maybe even a day or so like I did. I was able to get the set screws out of both. The bigger adjuster knob came off easy the fine adjust was a B*tch. I was able to take some vise grip needle nose pliers and was able to clamp onto the shaft to make sure it didn't turn and was able to take a small hammer and tap on the handle to get it to turn on the shaft to get it to slide off this was after I got the set screw out. I'm not gonna lie this probally wasn't a good idea but I didn't want to cut it off and buy a new reostat I scratched the face plate a little but it isn't to bad. I will find out if it works when I put it all back together but I think it will be ok. I sprayed a ton of PB blaster on the fine adjust set screw and shaft. I think when I reinstall it I will put some kinda antiseize on it to maybe help it from not rusting onto the shaft. As Ksellon told me take your time and go slow and as Shad would say I go to slow but hey so far it is coming apart pretty easy.
http://www.billswelderrepair.com/ is one place to get parts Ksellon is the best she can help with alot and get you good quality parts to you fast. weldmart.com is one hybriweld.com I haven't delt with these two but Kaye at Bills is the best I don't think I've ever had customer service like that before. I should know I use to work as a mechanic at a ski resort bills is the best.
Chris