Clutch pivot boss on a 350 block until when?

I’m toying with the idea of putting an SBC in my ’58 Biscayne if the 235 turns out to be a dud. I know that a 283/327 will have the clutch pivot ball hole in the block to mount the clutch pedal mechanism, but up until what year did they have the boss for that in the block for a 350? Is it only the Vortec 5.7 that doesn't have the boss?

 

Well I put an '87 block from a P20 van in my El Camino and it had the hole for pivot ball. Had to chase the threads but it was there.

 

I suspect they would be there up untill at least the mid 80's, when GM started using hydrulic clutches.

 

bttt