Speedo pinion gears

I'm looking into getting my speedometer re-connected. I have a chart that indicates a 2538945 to be used for a 4.56 gear w/26" tires.

While looking for that yellow gear on the web, I found several instances of other charts that list the -43 (blue) gear for that combo.

My chart lists the -43 (blue) to be used for a 28" tire with a 4.56 gear.

Which one is closer to 'right?

FTR, I'm running a 4.56 gear with N50-15 MT tires that indeed measure 26.5", manual trans. IIRC the trans came out of a '73 car. I DO know it's the smaller diameter mainshaft 'cuz I had to change the prop shaft when I put the trans in years ago (took out a '69 manual).

Any input would be appreciated..and a source for the gear, too would be great. I haven't found one, yet.

Thanks!