There has been a bunch of chatter about this on this website.
You will find a lot of info by doing a search. Basically, yes you have to cut off the end of the input shaft & the brg. retainer collar. Use the old trans as a guide. You need to cut the splines that the clutch disc rides on back about 1/2 in. to keep the disc from hanging up. The best way to do this is slid the disc on till it stops. Mark it on the shaft & grind the grooves till it goes back about 1/2 in. A cutoff wheel works good for this. Drill out the mounting holes to 1/2 in.