doing a carb swap on an 88 5.0, and the efi distributor has about a 1/2 longer shaft for more engagement on the oil pump driveshaft. Every other distributor we have has the shorter shaft, and I am not sure if we should run it or not. summit lists 5.0 distriubtors from 1968-2001 with no differences, same with oil pump driveshafts. i doubt a roller block has different dimensions.