dial caliper time
I've bought the speedway adaptors and they worked fine. sometimes tig welding them, sometimes using the set screws, First tighten the set screw to make a mark then drilling an indent for the set screw to seat, then locktite and double lock nuts on the set screw. Chevy astro vans use a compact DD shaft. and ujoints. I used a couple hooking up the steering on the willys.