Back in the ‘90’s I got into mountain biking and bought an nice 1998 Specialized Stumpjumper M2 Comp with Shimano XTR components. I’ve recently broke it out and now feel the bike is too small. The seat is at max extension and I’m bent over too aggressively for my 52 year old body. The frame is a 15.5” and I’d like to just get a 17” frame and swap components. What would be a good frame to do this with to keep costs down?
Looking at the bike's spec list at Bikepedia.com, you have a 30.9mm seatpost, 31.8mm front derailleur, 1 1/8" steer tube, V-brakes and a thread-in bottom bracket.
One problem with your plan, is that getting a 17" frame only effectively changes one thing: it puts the bars further from the seat. Your fork and stem define where the bars are, and if your seat height is currently correct, the taller frame will simply come further up the post.
Possible solution: to get a stem that has rise, and possibly a riser bar, along with new shift and brake cables & housings as needed by the new position, and then see if that gets the job done. Alternately, you could stick your parts kit onto a stock Specialized Hardrock, which is a more recreational riding position.