403 rear axle strap bolts

[guymd]

If you think the captive nuts are likely still good, you might try drilling out the centre of a broken bolt with a sharp, well aimed bit whose diameter approaches the threads without quite touching them. Or start with a narrow bit and follow it with a wider one. Then poke at the hollowed out fringe, working from outside toward the middle with a hammer and tiny screwdriver to make it fall away from the nut. Once an edge of the bolt starts to break away, it gets easier and the bolt collapses inward. I've done this successfully myself, but not on a car. The quality of the steel may make it tough to drill.