The 63C head was a centered head. The 63 was an offset.Not really sure why it was made though. Check E Bay and do a a Massey Ferguson search. There have been quite a few manual in there lately.
The 63 offset head was made to fit on a MF510 and allow the combine to straddle the corn stalks. The 63C was made for the 750 and 760. The 63 offset will fit on a 750, but the wheels will not run between the rows. If you could get an 1163 head it would be a big improvement over the 63. Good luck with your combine.
Yes I have a parts manual for the late model MF 750 combine as the combine burned and no longer need it. I have some of the combine bearing numbers cross referenced so you can go the local bearing store and buy them cheaper . We had this combine for 17 years and the book has quite a bit of experience
I have a late model grey cab 750 parts manual I posted it today somewhere else . We had MF 750 for 17 years. Some of the more popular bearing I have cross referenced their numbers so I could buy them at the bearing store for less than half of dealer price