You didn't start your question with the sentence:
"I am the CIO for one of the largest HVAC manufacturers in the world."
So the answer is: I hope you either have a family tie to the company, or some other mechanism of having your voice heard.
Since you already have shown that the path is chosen and the consultants are already on the ground running with the conversion, then it's already too late.
See, really your problem is that you hired in people that don't know how to do the job, and that's the problem with the majority of consultants these days. If you have good people (consultants or internal) then good things are possible no matter what choice is made. If you have bad people, it doesn't matter either.. the outcome was based purely on whether you have the knowledgeable people in a decision making role and in positions to actually do the work.
It's pretty much hit or miss on successful or failure ERP implementations, the common thread is the people and management. Unless that's fixed, get ready for a rough ride.
There's one thing that I try to keep in mind, though, when traveling down the rough road:
Change the things that you're able to change and position yourself for the change that you can't. So that way, even though things don't go your way, hopefully you have a backup plan that is still possible in the event of failure.