[RankingMember]

Propane or MAPP gas torch. Heat what the bolt goes through until it's cherry, then wail on it with an impact wrench. The torch is often referred to as "the big red wrench". Also, don't underestimate the power of soaking the stuck bolt in penetrating oil.

[rpcope1]

Even better than any penetrating oil you can buy: ATF + Acetone[1]. Also, having a rosebud torch with Oxygen + Acetylene is a must if you find yourself dealing with rusty bolts often.

[1] - http://www.jalopyjournal.com/forum/threads/penetrating-oil-s...