Quote Originally Posted by Brammer View Post
So I couldn't just take out the tranny and put an HD one in it's place?
No. You'd need a new passenger side axle from a car with an HD. You'd need to either swap the flywheel on your engine to a L67 flywheel or swap the TC in the HD trans with the one for your trans or they won't bolt together. And, you'd need to get custom PCM programming done so your PCM will work with the different gear ratio of the HD transmission.

There are a few smaller things to watch for, but that's the jist of it.