Hey Brandon,

I'm not going to input on your questions about vintage models, since I've never owned one. I'll let the other guys who have jump in here.

Regarding the Martins similar to the OMJM, I would say the three to consider are the OM-28, the 000-28, and the 00028-EC. I think the OM-28 is a very similar guitar, without the signature, making it go for much less money. You can usually find a used one for around $2000, sometimes a little less.

Hope that helps!

- Tom