Hi, I am in the middle of putting a basket case 1978 yz 80 back together. The shock is pretty rough and does not appear to be serviceable. Ebay has some but, I imagine any 40 yr old shock is going to need service. What is the chance a modern shock with the correct length and spring rate could work? If I have to buy a replacement, I would rather by a new or newer shock rather then spend money on a old shock that is no better then what I have. FYI 1978 was the first year for the mono-shock, and has the same set up as a RT100 or pw 80, its is a triangle shaped swing arm with no links, the shock lives up under the seat. 1978,79,80 were all almost the same.