After re-reading the pages you posted silverbullet, it pretty clearly states that the emissions configuration must match. In other words if you're throwing in an LS series engine, you have to have two catalytic converters with pre and post cat O2 sensors since that's what the original configuration was-who they are made by is of no concern as long as they are functional and pass muster. I think your DMV tech is trying to be difficult to discourage the swap since it's a buttload of work for them and they seem to think they're liable to some extent. I had this same problem with getting a camping trailer I built assigned a VIN number. I had to fight a little, but after a little talking and show and tell, they were appeased and everything was cool. In the EPA letters example they throw a chevy 350 into a 1985 Jeep-there's no way they are fitting the stock exhaust system length of a donor 350 into a Jeep without modification. The EPA seems like they are more general and just want the vehicle not to be a smog belching travesty. The DMV seems like they are interpreting the facts to suit themsleves and incorrectly interpreting the spirit of the EPA's memo. It's just going to be something that we go round and round with them on. They can be irrational pricks, but they can be reasoned with using a little common sense, logic, and the pages you provided with highlighted exerpts detailing what the policies actually are.