All small blocks share same crank ?

Only if you have a 2 piece driveshaft with a slip yoke in the middle. Trucks yes, cars no unless someone cut a yoke off and welded it back on in the wrong place.

I use to make pump driveshafts for tanker trucks. Would measure them, cut, put the end on, weld them, install and test.
We called it timing the driveshaft when you put the end on. We lined it up straight with the other end.