We just hardnose the front, weld the bumper straight to the end of the frame. And the rear we weld the bumper to the shocks, unless we run an FMJ body, otherwise it comes off

Here is a reusuable (bolt on) set up I have used.

Then the shock gets welded to the end of the frame. After the car is done you unbolt it and bolt on a new shock then repeat. That is a full seam welded 74 impala bumper that has been on three different partial weld Fords. We are not allowed any frame welding, kickers, DP, etc. So the bumpers outlast the cars and I got tired of doing all that grinding just to start welding again.