I may have an imposter. It's a New Process A833 that came out of an early eighties GMC pick-up. Straight through,1 to 1 ratio is now third gear instead of fourth, and what was third has it's gears switched around so it's now an overdrive about .7 to1. The little shift lever on the outside of the case is on up-side-down so when you put the gearshift into the usual third gear spot you get 1 to 1 and then the old fourth spot gives you OD. The shifter is like other shifters, but with a GM mounting bolt pattern. I have robbed this shifter and put it on an ordinary A833 Dodge 4 speed, but I have to drill one new bolt hole.
I have never heard them called imposters before. The only complaints that I've heard are, first gear is pretty fast, and there's quite a jump in speed ratios between second gear and third. This transmission should be tougher than nails, but coffee-shop hot rodders will always have heard of some wreck.