Early vs Late 3v Crank Pulley Differences?

Well I don't want to butcher any rare parts that someone else could use, that's for sure. I'll see what the largest diameter pre-70 2 groove I can find is. My math tells me that the cast iron pulley (156mm) I bought will give my WP (145mm) a 7.8% overdrive, while my original (187mm) was about a 28% overdrive. I'd love to be above 10% at least but I'll probably go ahead and put the cast iron pulley on for the moment so that I can get this engine break-in started.