OK Jon,I went by me diesel shop this morning (which I shamelessly plugged with his business card) and Ronald gave me the low down on the CAV pump. The 4 and 6 cylinder pump is the same housing, and the top cover is the same on all of them.
Pump 3 shows an end view where your gear would attach on a 4.236- driven by gearing in the front cover.
Pump 4 is an example of a "Cover Kit" that Ronald sells. The o rings are 2 different covers- but he told me that any quality o ring you could purchase would work fine.
Pump 5 is an over flashed pic of the data plate, but you may be able to see the bottom line of the tag reads PS61/850/6/2640. The important number here is the 6. It is the governor setting code.
Pump 6 is the chart that shows how to use the code. On the unit in our picture we are in
location 3 on the throttle shaft link and
location 2 on the governor arm. If your spring were to come loose you will know where to reinstall it I added this information for Charles
This may not help you now- but hopefully you can use it on your next reseal job.