RE: O.S. 70
Hello; Doesn't the Surpass II have black rocker covers? I think the cast numbers are different as well. I don't have a "II" to look at but the 91 II has a nipple on the intake pipe for the engine vent, and I think the 70 has that nipple too.
It shouldn't be too tough to buy a new head and swap it all over. A friend gave me the remain of his FS 26 surpass. He idd an inverted pass down the local road and shaved the head down on it. The rocker cover is gone and the three mounting screws have been torn out leaving the screw holes ripped out. Oh yes, the crank was visibly bent as well. I have to decided to keep the engine for parts, as I have 3 others. I'm sure it would cost more to perair the engine then to buy a new one.
If you dedide not to repair the engine let me know, I'll buy it for parts, as long as the crank is straight.