While Marlin has changed their rear sights to folding buckhorns, I don't know if the elevator has changed, so you may be able to get away with a new one.
There have been some differences in buttplate dimensions over the years, so my suggestion would be to remove your existing buttplate and take some measurements off the stock (not the buttplate!) --- then compare those dimensions with the buttplates listed here: h ttp://vintagegungrips.net/mabu1.html
When you have the measurements, send me a PM and I'll look through my spare Marlin parts to see if I'd have one that works. Alternately, you could purchase through the above sight (Vintage Gun Grips) or Brownells --- I've dealt with both and been very happy.
All replacement buttplates will require some shaping (simple filing and sanding) to bring into line with the stock. You may also want to research if your vintage rifle had a white buttplate spacer --- those are easy enough to make, and there are some good tutorials on sights like Marlin Owners. I have some white spacer material if you need it.