[Christ]

The language in the abstract actually warns against swapping between manufacturers because it could be costly to create a certified configuration using all the proper emissions equipment for the certification.

In reality, ANYTHING can be smogged and pass, regardless of whether it's a custom configuration or not, California or not. That doesn't mean it's easy. For the most part, you're basically limited (usually financially and time wise) to basic switches that are part of an already certified configuration, which means not switching between makes and models, etc.

I did misread that, though. It's not specifically illegal to swap between manufacturers, just generally not doable.

And then there's this tidbit:

It should be noted that while EPA's policy allows engine switches as long as the resulting vehicle
matches exactly to any certified configuration of the same or newer model year as the chassis, there are
some substantial practical limitations to performing such a replacement.

Which is what tells me that you can't swap between manufacturers without special regard, since the entire chassis/engine/emissions package must be a certified configuration.

Rereading it, though, it seems that the chassis is only used to designate the year, and thus, the emissions regulatory status, of the swap. (OBD status, actual equipment checks, etc.)

So in that case, you'd be correct.

You may resume the 6.5 Civic. I want.