Help with Prop shaft centre bearing

[Lippyp]

I have a 67-½ ton long fleet and need to replace the prop shaft centre carrier bearing. I have been told that there are two sizes of bearing. Would these be dependant on original engine fitment (I6 vs V8), weight ( ½ ¾ or 1 ton) or do they vary randomly. It is currently fitted with a 350, and a TH350, but was originally a six, tranny is probably original.

Is there any way to tell what size bearing I have without dropping it as I can’t get a vernier gauge on it to measure it in place. If I have to drop the shaft and measure it how easy is it and how do I do it, I’ve never worked on a vehicle with auto transmission and it looks quite a different set-up to what I am used to on Manual British cars.

Thanks for the expected input