Beth,
You may already know these places, but check them out for parts.
Hamiloton Bob's.
http://hamiltonbobs.com/cart/search/...cub-lo-boy-mm4
HB's is probably the best source, as you can get package deals for the clutch/driveline stuff.
Steiner:
https://www.steinertractor.com/Inter...T=57A6D7EB4ECD
Steiner doesn't offer package deals, and prices are comparable.
All States Ag Parts doesn't carry too much for the LB's but what little they do have is a bit cheaper. Might call them. They may be able to get more parts than they list.
https://www.tractorpartsasap.com/int...ts-s/84339.htm
Be sure the check ebay too. Sometimes you find a little better pricing. The driveshaft is the most expensive part. The clutch stuff isn't bad. Neither is the trans brake. Let me know if I can help. I've been into that stuff a few times.