The federal law states that motor vehicles CAN have a swap as long as it is an EPA approved motor/ configuration, your model year or newer and your weight class. Isuzu and Cummins are therefore, letter of the law, illegal. They are on highway EPA legal BUT they come out of heavier class of vehicles, not light duty like our Cruisers. A V8 swap is completely legal under the EPA as long as the emissions controls that came on the newer engine is swapped over and are functioning and the emissions arent "adversely affected." Locally, theyll probably still test it as your year model vehicle so if you can make it pass for your standards, the motor will work. If its a diesel youre doing, its all up to your DMV and the inspector. If he knows and cares, youre in trouble. If he is clueless and can just verify that it is a diesel, the title will be reworked and reissued as a diesel.
From the EPAs "Engine Switcher Fact Sheet:"
"EPA received many questions regarding the application of this law to a situation where one engine is removed from a vehicle and another engine is installed in its place. EPA's policy regarding "engine
switching" is covered under the provisions of Mobile Source Enforcement Memorandum No. lA (Attachment 1). This policy states that EPA will not consider any modification to a "certified
configuration" to be a violation of federal law if there is a reasonable basis for knowing that emissions are not adversely affected. In many cases, proper emission testing according to the Federal Test Procedure would be necessary to make this determination.
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For light-duty vehicles, installation of a light-duty engine into a different light-duty vehicle by any person would be considered tampering unless the resulting vehicle is identical (with regard to all emission related parts, engine design parameters, and engine calibrations) to a certified configuration of the same or newer model year as the vehicle chassis, or if there is a reasonable basis for knowing that emissions are not adversely affected as described in Memo 1A. The appropriate source for technical information regarding the certified configuration of a vehicle of a particular model year is the vehicle manufacturer.
For heavy-duty vehicles, the resulting vehicle must contain a heavy-duty engine which is identical to a certified configuration of a heavy-duty engine of the same model year or newer as the year of the installed engine. Under no circumstances, however, may a heavy-duty engine ever be installed in a light-duty vehicle. (Isuzu and Cummins 4BT)
The most common engine replacement involves replacing a gasoline engine in a light-duty vehicle with another gasoline engine. Another type of engine switching which commonly occurs, however, involves
diesel powered vehicles where the diesel engine is removed and replaced with a gasoline engine. Applying the above policy, such a replacement is legal only if the resulting engine-chassis configuration
is equivalent to a certified configuration of the same model year or newer as the chassis. If the vehicle chassis in question has been certified with gasoline, as well as diesel engines(as is common), such a conversion could be done legally.
Another situation recently brought to EPA's attention involves the offering for sale of used foreign-built engines. These engines are often not covered by a certified configuration for any vehicle sold in this country. In such a case, there is no way to install such an engine legally. EPA has recently brought enforcement actions against certain parties who have violated the tampering prohibition by performing
illegal engine switches."
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