Can anyone tell me if the steel seat bases on the earlier bikes (mine's a '73 250) are tapped for the hinge and latch bolts?  Or is there a nut on the other side?  I want to remove my latch, but not if the base isn't tapped...
Thanks!

There is a nut welded to the base on the other side .
However if the seat cover has been damaged allowing water in , corrosion on the bolts could be an issue .
I've snapped off a few trying to remove them .
Equal measures of penetrating oil and patience might be required .

Yes, very likely the bolts will snap if corroded. 
 

Thanks guys, I appreciate the quick responses!

It's quite straightforward to drill out the snapped bolt up to M5, and then tap a new M6 thread. Even easier if the seat is apart and you can get the base under a pillar drill.

Mine's pretty clean, no apparent corrosion. I sprayed a bit of Kroil, just in case. Going to try them later today. I am trying to save the original seatcover - that was the driver of my question, so really don't want to take the whole thing apart...
THanks for all input!

The corrosion can be on the bolt threads protruding above the nut . If the bolts loosen a bit ,
keep adding the Kroil and work them back and forth , and hopefully you can remove them intact .