I will probably add a couple bolts in the top. You're right though - easy to add later (which is why I haven't done it yet). There are no factory bolt holes in the top of the frame.
Trans mount is 1.5" tube, with 3/16" flanges, 3/8" bolts. Driveline is about 3° down, and none of the driveline is below the frame. I will -probably- have to modify the top of the frame "X" (and cab floor?) for driveshaft clearance.