Someone in another post had a link to a special horseshoe shaped bracket with posts that mounts onto the old post location and the lower posts on the horseshoe adapter are then in the right spot for 26 inch wheels as I recall. No idea of who or where, sorry.

You'd better be sure that the frame DOES have a really high BB location because unless you're using fat 26 inch tires that reduce the final height reduction pedal strikes in the turns will become a very real possibility.