The '68 standards were the infancy of controls, so it's pretty much numbers from the sniffer. I don't recall what levels of NOX or HC, but as compared to newer vehicles, they were pretty easy numbers to hit with a mechanically sound engine. The '68 standards are pretty pointless for us now though. About three years ago a modicum of common sense popped up in our requirements. They made the exemption apply to any vehicle over 25 years of age. So to use Dano's example, in five years his "83" will become exempt. The other twist in Washington is that emission checks are only done in the more populated counties. Again, it's based on extortion from D.C. linked to dispersal of "Federal Funds". The trick some guys used was to get a P.O. box in an unregulated county and use that for their registration address. Well, now with computers, they've clamped down on that and do cross checks for county of residence. If that doesn't work, then the person trying to use a P.O. box has to prove where his actual residence is.