So it's not possible someone between 1972 and you obtaining the frame, cut the mounts for shocks off (maybe to install a shock hoop or rear inboard shocks or??), ground them smooth?
I know all production Broncos had shocks, so therefore had shock mounts... but...maybe it's not a production Bronco frame - Are there both VINS on passenger side
frame rai? One midship, the other by belhousing/engine jct. Maybe order a Deluxe Marti Auto VIN report - it will tell you sale date, buck date, build date, schedule date, and selling dealer.
Then you can confirm it was a production Bronco and would have had shocks on it..... And someone between new and you getting frame, ground off the mounts, but did a better job than most Previous Bronco Owners with a sawz-all and beer.