as stated the epa hurdles would require in excess of 50k dollars, however
it likely would take a half million bucks to do the alternations to a lister to make it have a chance at passing the first time... and that is one engine!
if i recall you must submit 3 or more such test engines to the epa for testing.
there is a reason the big boys are injecting urea, use special catalytic converters, particulate filters, computer controls, all on engine's that were light years more advanced than a lister to start with.
basically it ain't never going to happen.
anyone tells you different, better hide your wallet!
bob g