Done!
The shop owner opened the shop to let mee see it again on a sunday, now that's good service in my book.
Ended on $450, I'm happy with the deal.
A close inspection and it turned out to be all original parts, only the choke had rust enough to be considered dangerous.
1973 model MK1 superbass, but with a solid tagboard - so that's basically what i wanted.
The chassis was shitty dirty on the outside, but as new on the inside. Every solder point had their red paint seal/dot.
Can't wait to get home to fire it up (but first - a trafo insulation test, of course)
Thanks for the input here folks, I'll post a pic when it's home - my cellphone is about the same age as the marshall.