The tag will not tell you much. A"B" number motor could be the original for many reasons. JD may have bought a large amount of B engines in late 1966 when the 1967 models were already out and used them up in the year 1967. It may be a replacement motor after all it has only been 47 years since the tractor was built. When I worked for JD starting in 1975 we were regularly replacing short blocks and engines in the earlier tractors. One of the CC forums had a vendor selling replacement tags at one time but you had to add your numbers. Kohler does not. Roger