I deal in restored TF tools and have rebuilt quite a few wood framed boring machines. First, check the tightness and parallelism of the 2 main base pieces. You may be able to restore the correct spacing of the vertical rails by either tightening the 2 base cross bolts or by removing some wood from one of the 2 small wood base cross pieces. As far as the stripped hole, I usually drill the hole out slightly larger then the screw, say 3/8" and epoxy a dowel plug into the drilled hole. That just about always works.

If you end up convinced that you need need to replace some or all of the wood pieces, it's just straight forward casrpentry. If the verticals are 7/16" mortise and tennon with the base, make the new ones with 1/2" so that you can cut the slot in the base with a standard, readily available, mortising bit.