Re: woods 60 vs. 600?
most any slip clutch needs to be broken loose before you use it or it may not slip at all, as has been stated already. They tend to rust solid and then will not release when they should. If you are doing nasty work with a slip clutch implement loosen up the clutch enough to let it slip and burn off the rust (don't burn it to the ground here, but get the rust worn off) or it may not protect the pto drive when it should.
Answer for Woodbeef
The blade pins on your M4 should drop right out after removing the holddown clips and keyhole blocks. Generous quantities of heat & beat will help. Never-sieze on the way back together. Good luck.