First, I was going to pay the money for a set of genuine M715 tow bar adaptor feet. I waited and waited several months and none ever seemed to come up for sale. Then, I decided to build my own. That idea lasted as long as my cut off saw motor. Finally, I realize I was surrounded by M35 parts left over from the Gasser build.
I didn't want to cut up any of the good and probably going to be used on something else M35 front shackle mounts. The M35 rear shackle mounts though are smaller and will fit on top of a M715 bumper. The only down side is the rear M35 mounts have a 7/8" hole in them. I didn't want to bushing it down to 3/4 which would have been the easiest and fastest way to do this. Instead, I bored them out to 1 inch figuring if I had to have them on a M35 again, they would still work as a safety chain holder.
My front M715 bumper is actually a converted piece of 6" channel iron. Very thick and strong compared to a stock M715 front bumper. I used the top frame to bumper bolt as one of the bolts for the shackle and drilled another. Here is how it came out right after I drilled them. Those are 1" tow bar feet on the mounts in the pictures. I painted the mounts last night and should have them on the truck tonight in final form.