...but how?

I'm in Texas and we get yearly inspections. On anything older than a 1986 model you must have a catalytic converter. How do you deal with inspections and emission crap on one of these conversions? I know its different from state to state.......but still

Off the top of my head... and if I remember correctly....

Most states allow an owner to convert a gas vehicle to diesel power. Those that require emissions certification usually require that the engine be the same model-year or newer than the vehicle it's going into, and the engine must pass the emissions certification its model year. For example, if you installed a 2001 Duramax into a 1989 Chevy pickup, the engine must pass emissions for a 2001 model year Duramax 6600, which would include all of the exhaust aftertreatment devices if vehicles with that engine had them in 2001.

California and some northeast states are tough on emissions. Most other state's emissions techs wouldn't likely know enough to cause a problem for the owner.

Those states that don't currently test diesels still fall under the umbrella of the Federal EPA, but those trucks aren't tested, and can drive anywhere in the country if licensed in a no-test state. Montana doesn't test gas or diesel. Law enforcement here in MT can write "fixit" tickets for any smoker, however.

Check with your local DMV before beginning a conversion to learn what hurdles you might run into.

As far as I know, all states require a change on the vehicle registration to reflect "diesel" if the vehicle was formerly gas powered. I'm not sure why that's important, but it is here in Montana.

Jim