Is a GMC truck just a dressed up Chevy truck?

The SAME gotcha applied to IHC engines. In the mid 70's IHC put 401 AMC engines into their products, but IHC ALSO made a 401 V8. SO THEY RENAMED the AMC engine a 400 for differentiation. BUT "smart" mechs would raise the hood, say "oh that's an AMC 401" and go order parts. Well They were actually ordering parts for an IHC 401 so THEY DID NOT FIT

I actually got into a heated discussion about this a few years ago with an avid IHC 'expert' but he called me on the phone later, and said I was correct.