SO, apparently old cars and trucks are not "grandfathered" (exempt) from emissions regs? That surprises me a little. If I remember my chemistry CO is a by-product of incomplete combustion. Improve the combustion and lower the CO. Have you had the truck very long? Has it been tested before? If so, I guess this is the first time it was over limit? I would say a fresh tune-up with a hot plug, the timing advanced as much as possible and still not ping, and as lean a carburetor mix as possible. Sorry, I don't have to worry about that in down-state Illinois. Let us know what works. If anyone thinks I'm wrong please correct. me.
