just stick a wood shim on top of the frame when you cut the tube out
my son drove his 68 elcamino from new hampshire to detroit, heading out to seattle
he asked me to help him patch some holes in the frame near the steering box
when we pulled the bolts out: 1 was similar to yours and 2 of them were rusted to .2'' (broke at first turn)
we were mildly shocked to say the least
summit carries them
summitracing.com/parts/opg-c240404