[GMCNUT]

OK, so since accessory options on 55-66 trucks is my bag, I will tell you some of what I have learned so far. First, you should know that literature for 55-66 GMC's is in very low supply in the first place, and GMC relied more on its dealers and their black-and-white line by line printed accessory order sheets than from anything you could hand out back in the day, so unlike Chevrolet, GMC accessories were never marketed with much supporting literature. The dealer salesmen had quite a bit of info on them of course, but not much has survived the way you see for Chevrolet. So, with that said, in regards to 1960-66 GMC's specifically, the accessory guides are all pretty much reprints of one year to the next with the covers being about all that changed. So aside from the hood jet in 1960-61 all the remaining accessory options stayed the same throughout the 60's until 64 when assembly-line A/C was first offered. Both Chevrolet and GMC offered assembly-line installed A/C starting in 64. Many people incorrectly state 1965 was the first year for this option. Dealerships installed under-dash A/C units made by a variety of manufacturers starting in 1958 through the 60's. Dealerships could also install the assembly-line "all GM" A/C as well, so very few 64-66 GMC's actually got ordered with this option. Factory power steering began in 1956 and was available through the 60's as well. Factory power brakes came out earlier than 56 but I cannot remember what year. Factory Automatic transmissions started in 1953 and were available as cast iron 4 speed Hydramatics until 1963 when the Aluminum Chevrolet Powerglide was adopted to reduce vehicle weight. Factory installed and dealer installed accessory guages were available too - Clocks and tachs started in 1953 or 54, and were available through all the 60's models. Starting in 1960 you could get an optional Ammeter, Bat-O-Meter, Volt meter or oil guage. It is rare to see a 1/2 ton truck with a Voltmeter or Bat-O-Meter however, as these were primarily installed on trucks that came with more power consuming equipment and had heavy duty generators and alternators. The Ammeter and Oil Guage were the most commonly installed guages on 1/2 ton thru 1 tons. The Clocks were used on all models but most commonly found on 1/2 ton thru 1 tons. Tachometers seem to be evenly added to as many 1/2 to 1 tons as to the bigger trucks. Factory installed or dealer installed Hazard Switches began in 1958 and continued through the 60's. Accessory Rear heaters were available on Suburban models starting in 1964. Glove box lights were available from the early 50's through the 60's. The dealer option compass was available from the mid 50's through the 1960's. Every other option was stuff like you see in the accessory guides - mirrors, seat cushions and covers, spotlights, road hazard flares, roof marker lights, etc....not sure any of this info really helps you or answers your question, but PM me if you need to know more specifics.