Yamabond JUST the cover's sealing surface, oil the other side of the gasket, assemble. Resist the urge to over tighten the bolts. Hope that works for you. If it were me, and I do this fairly often, I take a long flat file and VERY carefully place it across two areas of the sealing surface and lightly stoke, constantly moving it around the whole cover so I take just high spots until I see file marks everywhere. OR and this may be better, put some say 320 grit on a FLAT surface put the cover on it, work it it circles, inspect to see where the low spots (gaps in sanding marks) are, see if you can make them go away. Then assemble as above. For either method remove the oil pump first clean cover completely before assembly.
Yes the covers interchange, well there is a year or 3 with more clutch plates that has more clearance for the clutch pac? but that wouldn't bother a 73. Some of the late model covers have an oil sight gauge but it doesn't hurt anything. Interchange shows 1970 to 1980 fit I think the 81-83 do also. the 83 cover shows it fits back to 1974, I am pretty sure it works on the earlier bikes too.
