[Jeekinz]

Buy an electric shear/nibbler, a sawzall is going to warp the snot out of the metal and leave a rough edge. Second to a shear would be a jig saw with metal blades. Id never use a sawzall on something i wasnt gong to scrap.

 

[Jeekinz]

I'll try some grinder cuts as well. I ha e some of those green diamond coated cutting discs, which are truly a beast on steel.

Ive done metal fab since 1992. You dont need special cutoff discs. Buy in bulk. And yes, if cutting through frame or structural areas maybe a sawzall will work for you. In that case you want good blades but a cheapo tool will work fine. Only thing to look for is to make sure its toolless blade change.
Also, I like to have 2-3 grinders setup with different discs (cutoff, flap, grinder) it gets to be a hassle changing all the time. You can buy grinders from HF for $20 and they're good beaters.