earliest technology was manual for everything - I'd think the difference shifting to automatic is simply that the cars were getting aimed more at "suburban housewives", while the trucks were still aimed at farmers and tradesmen who knew machinery and didn't wanna spend more than necessary - hand choke goes right along w/ hand throttle, which also disappeared on cars way B4 trucks - main thing is cheaper prolly, but GM also tended to use up stock on hand on the trucks - auto chokes on trucks started happening w/ the V8, and the trucks started being marketed to "surburban cowboys" ie: Cameo design
Bill
