I picked up the seat and a later 'sister' seat from the blasters today. Chemical cleaning just wasn't getting into all the corners and areas of damage.
I've now got all the damage exposed and a good example of what it should look like.
Underneath is the major difference as the '61 seat has bolted-on brackets and the side pieces appear to be welded on rather than being one big pressing. My main interest is in copying the 'tang' strips so that I can attach the cover in th ecorrect way.
These pieces are spot welded to the seat pan and I am hoping to get some new ones laser cut. I don't like the look of the available replacements so I'll do a drawing and get a quantity made.
My seat has lost virtually all of its tangs so I'll just grind that down ready for the replacements.
I'm also going to make and weld on some strengthening plates to reinforce the mounts. I realize why I have been putting this off fro so long.... :-)
G