If you don't need to save them just wrench on them until they either unscrew or twist off. They are only 1/2" bolts right?

Otherwise PB Blaster and time, or if that's not enough persuasion some serious heat should do the trick.

Grigg


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-