A few short sharp taps to the end of the stud with a hammer will help break the rust bond too - and thus help with the two-nut shuffle. put a nut on the end about flush with the top of the stud to avoid damaging the threads. Holding the cyl in a big vice is very helpful if your not doing this so far

Generally the combination of a bit of penetrating fluid, a few taps and maybe a bit of heat and some patience will get 'em out.