[07SSSC]

I went through a GM backed program called ASEP (Automotive Service Educational Program). It costs a fraction of those other two and you come out with GM certifications. Only downfall is it takes 2 years, and you do have other core classes like math, english etc, which I was able to test out of a few. Part of the program is setup so that you work in a shop while completing school which really helps.

We just had a new tech start up straight out of UTI, he knows a pretty good amount of stuff but he has spent a lot of time completing GM training requirements.

Since you're leaning towards body there is also a BSEP (Body) program which is the same as ASEP but for body work.

Don't know how many ASEP/BSEP programs are still around but it may be worth a look at, if nothing else just as another option.