I've got the same engine. Attached pic shows the balancer. As you can see, (if you look closely) the timing tab on the front cover extends out at least 1/2 the width to maybe as much as 2/3 the width of the balancer. I didn't take a pic of the balance by itself prior to reinstalling. I'll be glad to measure width and diameter if that would be helpful.
This balancer is original to the engine.
As a side note, I have seen earlier '60's vintage 327 balancers that are about 1/2 as wide as this one. Those would not be the correct for this application.