Early vs Late 3v Crank Pulley Differences?

Tylinol said

So the earlier pulleys have an extra groove? Mine has three grooves on the crank pulley, which I thought was the same number as the later cars.

Click to expand...

I took the 3 Groove pulls of my 66 273 ac Sat and put them on my 70s 340. No problem. But I used them all. And the water pump pulley IS right on the crank pully. Think it's was sparking once (.self clearance)