tranny is the same, the same basic schematic is the same, the board layouts were different. As they made more the caps went from 5900 to 7500 to 9800mfd. the 22,000 mfd's fit fine. I have noticed the tranny sits deeper in the B chassis than the Ser I's (on some) there are spacers to to bring the tranny out of the chassis further. on the ones with a deeper set big caps may interfere with the meters, but can usually be made to fit. No problem on this B as it has the recessed curves in the tranny case for the caps to set in. he 22, 000' s fit very nicely. When I finally do one of my "B"'s I'm going to take advantage of Joe's independent power and grounding design of his board and take a tranny out of one of these junkers, redo the chassis to hold 2 separate power supplies consisting of a 700 tranny for each channel with 4-22,000mfd caps and a 35 amp BR for each side. Kinda like a Spec 4 on steroids. Withe Joe's board you can actually drive each channel independent of each other, crosstalk should be non-existenmt. not that it's a factor now, but can you imagine?? A big fat tranny on each outside back corner with a trunkfull of caps??