I have a AA plate #711112ns that mated a T18 and a dana 18 tcase. I dry fit it to the sm420 I just picked up and it looks like it fits. Some of the extra holes in the plate were sealed off. First question will this adapter work for Sm420 to 3 or 4 speed L.C. T case. I will need to pick up the spud shaft and other seals,bearings and etc. Is there any advantage or disadvantage to the AA instead of a plate style Sm420 adaption. Does any one recognise the AA part number? Thanks.