SB Single Groove Crankshaft Pulley

I'm trying to obtain that dimension... anyone on the forum have one that can be measured?

In summary, I'm told the single grove crankshaft pulley that I have currently is correct of an engine that contains a 69 or earlier water pump (cast). My 1970 340 has the aluminum style water pump that is throwing off the alignment using the 1969 and earlier crankshaft pulley.

Based on some parts books, it appears the 1821449 is the correct number for a single groove crankshaft pulleys.