Hello,
I'd go for it - re-chassis and rebuild it.
I replaced the chassis and bulkhead for galvanised on mine about four years ago...a word of warning, though - I also ended up replacing the seat-box, all the bushes, all the chassis brackets, the roof, the dampers, the steering-box, most of the interior...the list goes on. I also replaced every single bolt I took out for a stainless equivalent from
LRM and I stopped adding up the bills about half-way through.
It's
very hard, when you've got it all stripped down and you've spent ages cleaning and painting bits, to then bolt back on rusty old rubbish with rusty old bolts - if you can, you've got more self-control than me! I managed to strip and rebuild my Defender 110 in about 18 months, working on it every night and most weekends - I could probably have done it quicker if I'd just started out with an angle-grinder rather than a socket-set on the strip down
Good luck with it!