Identifying Gear Vendor units

[Ford420]

I know I've seen this somwhere in the past but can't find it now.

Is there a way to identify Gear Vendor and Lay**** overdrive units as P or J type by serial number?

I've tried searching for hours with no useful results. Thanks.

-Chris

[Blueknightcrew]

I've been doing alot of research on these things and I talked to a fellow that is very knowledgeable with them and he said there is a book that you can decode the serial # and tell exactly what it is and tell what time frame it was built. He told me:
Its very easy ,I have a serial number book……….but J type use a small speedometer gear ¾ to 1 inch diameter ,P type use a large one ,around 2inch diameter also J type use a very small rear yoke

P type use a standard th400 year yoke


Hope this helps, Any other ?'s let me know and I'll try to help.
I just got one for my F550 project.

Ron