I think the foot clutch may be slipping d-17

I have a  1960 series 1 D-17. When in higher gears the motor seems to rev up while on large hills and the tractor comes to a stop. If I put the tractor into 1st or 2nd gear it will take back off and pull the hill. I will also bog down when running the finish mower through heavy grass if I'm pulling a grade and I will have to go into the lowest gear possible. I did adjust the clutch pedal travel and that seemed to improve things a bit. I have read that there is a possible clutch finger adjustment through the bell housing hole. I can see the clutch fingers all touching the throw out bearing and when the clutch is actuated the throw out bearing moves forward and pushes them all in. My fear is I will have to split the tractor and replace th clutch. I bought it because it had a really nice loader, I was considering putting on my IH 656. I really liked this tractor and hate the thought of pulling the loader and sending it on its way to Craigslist and selling it for not much since it is not right. Any advice on something I may be overlooking would be appreciated. Thank you in advance.