If you do a few calcs to get the exact circumference of the part you want to measure, then make up a measuring rule out of say some steel pallet banding to exact length.
Then it would be a matter of wrapping it around the part and see if there is an overlap or a gap. Or mark up an over long piece and see if the loose end matches up to the mark. Or even wrap it around one end of one part, and mark it. That can then be used as a comparison on all the other parts, to see how close they are.

You can buy super flexible engineering rules that do exactly the same thing, for checking out large diameters, but I have forgotten the exact name for them. Not cheap though.

Bogs