I was wondering is it legal to swap an engine (cummins) that already came with a filter to an older truck so it could still be running legally 2014? Has anyone done it & if so did everything come out good?
Truck emission standards have to do with the engine model year, not the truck model year. So yes, you can do that. Getting the wiring properly sorted is the issue I've seen people mention elsewhere as being the main drawback.
True, emissions are tied to the engine, but that only has a broad connotation in regards to a glider truck. With a new production model, the engine must be within 1 year of chassis manufacture. So while, say, you could have a 2006 non DPF engine legally in a 2007 truck, you could not have a 2000 engine legally in the same truck, unless it was a glider kit truck. And, there is also a stipulation that the EPA standard engine that the original production truck came with must be the minimum standard for any engine swap. When I bought my 2013 FL glider and we dropped a factory rebuilt 2000 series 60 into it, it was an easy compliance thing. The waters get a little murky when trying to do these things to a regular production truck. Best to check with folks whose business is to keep abreast of such things, since the fines for out of compliance can be more than the cost of a new engine.