403 rear axle strap bolts

[mikebro]

I've got the 403 floor completely stripped out so have good accessibility to the rear axle strap bolts. The bolt heads are badly corroded. I have soaked all 8 bolts with WD40 over several days. However, as expected, the first bolt sheared off with very little torque. Looking at the break there was not much thickness of good steel left, and I fully expect the other seven to be the same. So, I am committed to a full repair which presumably means cutting out sections of the chassis rail sides with the captive nuts and broken bolts and welding in replacements..............or does anyone have an alternative cunning plan they could share?