Get a big pot of water, enough to submerge the body, and heat it to around 170-180° (do not boil). Have another pot of cool tap water ready. Dunk the body in theh ot water for a few seconds (use tongs!), remove, give a twist in the oposite direction past where you want it, then dunk in cool water. repeat as needed. Don't leave it in the hot water very long, or the plastic will shrink. I can't count how many Monogram NASCAR T-birds I've fixed this way, adn the ones still on my shelf are still straight going on 7-8 years later.
Brian