All stock chev dist are same length--sb, bb, and tall deck all have same length

do you have a spacer between the main cap and oil pump to lower the pump for a deep sump pan?

Tall deck truck manifolds had the dist setting lower----A few companies now make dist with sliding collars, but if your shaft doesn't mate with your distributor in the area of the boss you are asking for an big oil leak all over the track/road and a trailer /tow truck ride home