WE used to always cut them with a torch, I have even cut and rewelded them back together, the 49 olds rear end in the 31 chrysler had a small coil at the ends with a large washer and bolt to hold them in place. stock was about 6 inches too high. I don't remember which arc rod I used but it was expensive, Today they say use a die grinder with a cut off wheel. probably compress the rest of the spring then cut only half of what you think you need, release the spring clamp and and probably try again.