I suspect that the road triple may want 5mm more bottom bracket length as it was originally optimized for a 130mm rear spacing chain line. This assumes that you are working on a modern MTB with 135mm rear spacing.
Actually, it's a Redline road bike with 130mm rear spacing. I'm not worried about having a screwed up chainline as long as it gets me from work and back.
Am I to assume that this would probably work? I tried putting a double on the BB, but the small ring, a 42, came really close to rubbing against the frame, so i didn't even bother trying to actually ride it. It seems reasonable that the small ring on a triple would probably allow for more space between the chainrings and the chainstay.