They'll probably fit tire clearance-wise Most olde MTBs I've had will fit 700x23 no problemo.

Hurdles are rear dropout width, which could be coldset smaller, and brake mounting, which can take a little digging through the olde nutted caliper bins.

EDIT: Just looked at all pics and that ain't no MTB, dunno where MTB idea came from.

EDIT: Oh, 26" wheelset on there. I'm too tired to think. But yeah, frame good to go for 700c clearance-wise.