I've only dealt with 1966
and older. As far as I know, have seen, read or heard under no circumstances do you bore any holes in the frame rails themselves. The axles bolt to the side plates only, the 1/4 inch flatstock that is welded to the outside of the frame. Thats the purpose of the side plate, strenghten the frame at that critical weight point & provide an anchor point for the axle. I've seen the dexter instructions myself, pretty sure that part does'nt apply to our application. Yes we have to widen the slot for the modern axle. As far as the axle contacting the frame? Makes me wonder. The axle tube itself no. The mounting plate pre welded to axle tube should be high enough to contact the bottom of the frame rail. However I've only replaced originals with the Dexter "high Mount" option mounting plate, extra inch of lift. Barts right, a pic could clear it up.