I have got one of those cheap reciprocating saws from Aldi and I use the Black & Decker Piranha 153mm Bi-Metal Scorpion Saw Blade, and it cuts chassic up no problem.
As far as Oxy Acetylene goes, when i was in the Fire Service I went to loads of house fires where people has cylinders had problems house catches fire, and when they blow they will flatten your house and surrounding neighbours as well, also you might find that you wont be insured either.