Best Penetrant to Remove Differential U-Bolts?

Going to remove the rear end from the '65 Formula S in order to tip it on its side and paint the bottom floorboard. I hear PB Blaster is good (don't know if it's sold in stores around here). Any other recommendations? Thank you.

I'm surprised you haven't heard of ATF mixed with acetone. ATF is used in in rural areas. I save Dexron and mix a batch up now and then. Works pretty darn good. My 2 cents. Typed too slow. Brian beat me to it.