You may want to call a FE engine builder such as FE Specialties or Southern Automotive, or Kieth Craft and ask more about how important the heaver distributor shat is. You can also look at Summitracing on line and read about
oil pumps and
Oil distributor shafts.
This is from Summit Racing: Good insurance at a low cost.
These
oil pump driveshafts are CNC-machined from 4130 chromemoly and centerless ground to avoid stress risers. These race-proven shafts eclipse breakage-prone stock units that frequently fail when used with high volume oil systems, heavy racing oil, or high rpm applications. The ends are induction heat-treated to reduce wear.