As an AC newbie, would someone mind giving me the Cliff Notes version of the progression of AC tractors from the WD era though the D series and into the 100 series? From my uneducated eye I can see that a lot of the early tractor DNA appears to have carried over for many, many years. It seems like there's a lot of WD in a D17, for example. And the later 170 also looks like a D17 with different sheet metal. Am I on the right track here? Can someone point out what replaced/superseded what?
Also, of the D series, which are considered the best? Are there any to avoid? Were the diesels better than the gas burners? I see the diesel D17 was a 6 cylinder whereas the diesel 170 was a 4 cylinder, correct?
Same question on the 100 series. Which were the "better" ones and which were "not their best effort"? And which engines were better? What was the smallest tractor in this series to offer a 6 cylinder diesel? Which offered a console Power Director?