You got good service out of the O.E.M. clutch, that's tough to beat. I put a South Bend ConOFE in mine and regret it, shudders in reverse. My flywheel was shot, got a new one from Cummins, about $300 IIRC.

I think the crossmember has to come out, you'll need to spread the frame to get it out.
Trans is about 400 lbs, you're going to need help. 2¢

Robert