Hey Dude,
I'm assuming that you have the stock setup like the attached photo with studs in the head and the collars that bolt to it?
I typically use the spigots that bolt onto the head with countersunk screws and the pipes slip over them and "clamp" on.
For yours, the shells, #13, can be rotated back and forth to facilitate getting the Collars, #14, into place on the studs. I couldn't find a set handy to look at but I don't recall ever having to cut/gring anything to get them on. Maybe if all else fails, loosen the motor mounting bolts and pry the engine around till they slip past the frame? but again, I don't recall ever having too much trouble with it.
So I guess that does absolutly nothing to help,,,, huh?