does anyone know the difference in pitman arms??

I would agree, they are different shape, I had ordered a pitman arm from classic and when it arrived the shaft hole was 1.25 " while the pitman arm I removed from my steering box is 1 1/8" and its for a big block car. I may have a 67 pitman arm as opposed to a 68'?

67 and 68 pitman arms are the same. Only the idler is different. You got a pitman for a large sector steering box.

Steering Linkage

And while I won’t say this is exhaustive list, the folks at big block dart didn’t see to include a part number for a big block pitman arm...

Moog/Chrysler Suspension Part Numbers