@ #75: Emissions are met by having parts that work well over a given time frame. An IB Bullet with a modern high silicon low expansion piston, good steel rings and valve stem seals can provide all the mechanical combustion sealing technology you need for emissions compliance. The CSC folks are still using carburetors on their newest SC250's & TT250's, machines that make about the same HP as an IB Bullet. The Bullet is a low compression motor, so NOx isn't that big a factor. Spark timing was crank-triggered on the Electra, eliminating the distributor drive gear slop, if it was even a problem. You could indeed market an "antique", but you sure couldn't sell one to the prevailing crop of buyers. All the maintenance hassles you've enumerated and the 50 years behind the times performance level for displacement would squelch the deal. An "antique" is also labor-intensive to produce, with it's myriad of hand fitted items, so an EPA-compliant Bullet would likely cost more than a modern, "clean-sheet" design that would leave it for dead in about every category, especially regarding owner maintenance.