A little advice here please, I'm going through an old 22' 1973 Oday regrettably my Mainsheet system is in a shamble, missing line and blocks that have seen better days. Being relatively new to all this it's rigging is still somewhat of a quandary to me. Does someone have a good photo of the Mainsheet system and blocks used and how it is rigged on the 1973 model? D&R marine does have the Mainsheet w/block for the 22' Oday but I don't think it's for the 1973 model... not sure if it would be compatible. Thanks for any information. 
Terrence
Terrence