When technical writers write about the subject of nuts and bolts there oftentimes seems to be an infantile temptation to allude to the act of screwing. That said, we'll skip past the corny "No, not without a washer!" jokes and get right to the heart of things with a quick overview of what we would like CCT readers to leave with after they've read the following article: the ability to bolt their truck together properly without stripping threads, and to repair damage that occurred before they owned the truck.
First, we'll start with the metalworking basics a person should know before they ever tighten down that first nut or bolt on their truck. The principal of external and internal threads utilized to construct a vintage truck is an age-old subject that predates the automobile industry by several thousand years, but it isn't necessary to go back quite that far. A good place to begin in time would probably be in the early teens with Henry Ford and his proclivity for "bastard" threads. (In general, these are threads that don't conform to an accepted standardized system.) I'm bringing up the subject of bastard threads because the first thing for one to do when working with nuts and bolts is to determine which thread system they are dealing with. The thread classification most common-almost to the point of being able to say it's 100 percent present on original classic trucks-is the SAE (Society of Automotive Engineers) coarse and fine thread system. Enter into the mix a drivetrain derived from an '80s-and-up American-made platform dropped into a classic truck that has consequently been transformed into a custom classic truck, and the odds of finding metric nuts and bolts sprinkled side-by-side with SAE nuts and bolts are about 100 percent.
It's interesting to note that the effort (notice that I didn't say Commie plot) to force the United States to metricate began less than one year ahead of Russia's 1917 Bolshevik revolution on December 27, 1916, with the formation of the U.S. Metric Association (U.S.M.A.) at Columbia University in New York. It really doesn't have anything to do with classic trucks, but it was in 1925 that Russia and China switched to metric, while the Japanese began metrication in 1957. For the most part, or at least what I feel is relevant to automotive use, the metric movement was pretty much dormant until 1965 when the British announced they were beginning a 10-year program of converting to metric system usage. Again, I'm skimming the surface, but 1965 was also around the time the British joined what is now the European Union (EU).
Coinciding with the British metrication being fully implemented in 1975, the next time Americans were to hear about bastard threads, uh, metrication, was from another guy with the last name of Ford. It was on December 23, 1975, that President Gerald R. Ford signed the Metric Conversion Act of 1975, which for the first time gave official federal sanction for the U.S. to convert to using the metric system. Fortunately for the folks who weren't real excited about metrication, the 10-year deadline stating that conversion must be completed by 1985 was somehow dropped from the final version that was ready for the U.S. Congress to vote on.
Jumping back to the roots of SAE nuts and bolts: The SAE was founded in 1905, and the Society of Automotive Engineers introduced their own standards in 1918 with SAE National Fine (NF) and SAE National Coarse (NC) threads.
From 1918 until the present, without counting the false alarm during the '70s and '80s, SAE threads have been the national standard. That said, one cannot assume they have SAE threads throughout their classic truck, because it is entirely possible that the owner before them installed aftermarket reproductions manufactured offshore, or that a hack cranked in metric bolts. Regardless, the best practice when starting a new project on your old truck is to first establish what type your threads are, and what condition they are in before you attempt to bolt things together.
 The first step to determining...  The first step to determining which type of threads you've got (such as SAE or metric) is to use a thread pitch gauge. This is a Craftsman SAE gauge. |  If you can't determine what...  If you can't determine what the pitch is with an SAE gauge, the next step is to move on to a metric pitch gauge, such as this one from Craftsman, and verify if you are dealing with metric threads. |  This is a Craftsman SAE tap...  This is a Craftsman SAE tap and die set from the '70s. There is little to distinguish these sets from the ones Sears sells today. |