Whats your guys take on a front end conversion

Well it sounds like one of the cars was used to fix the other for some reason. Next I would try and figure out where the '76 "ends" and the '73 "begins", to see why the swap was done and if it was done correctly. Depending on where and how it was clipped it might be worth taking it to a frame shop and having it checked.

The other question would be the legality of the whole thing. But if you have a title that matches the VIN on the dash, and that matches the VIN's on the rest of the front clip, I'm not sure you have a big problem.

Officially, you can't legally remove a part of a car that has a VIN, but package trays and other parts with VIN's do get replaced all the time. How that gets handled varies state to state. When I registered my Challenger, which came from out of state, they checked the VIN on the dash, door, and fender tag. They didn't even check the radiator support, which would have been easy. And of course, the fender tag and door sticker are the easiest things to remove and change. I've had a couple vehicles need an inspection here, no one has ever checked the package tray.