When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I searched the entire FTE web site for 38633 and I find two posts. This post, of course, and one where they are referring to 38633 as a ZIP code in Mississippi.
Next, I checked both the 1957-1963 and the 1964-1972 MPC
38633 would have to be a base number or possibly a piece of standard hardware with an incomplete number.
1957-1963 MPC jumps from 31662 up to 40010 so there is no 38633 base number there.
1964-1972 MPC jumps from 32244 up to 40010 so there is no 38633 base number there, either.
NumberDummy has stated more times than I care to read - when asking questions to include the year and series of truck you are working on - to be accurate you'd also need the Warranty Number and possibly other details from the Warranty Plate.
It's just like you went into a Ford dealership and asking about a part. If you only gave them a strange number and no information about your vehicle they would just start to question you - no way could they help you.
Now, in this case we can possibly narrow it down to 1961-1966 but then there are people who come to this forum to ask about part numbers for their 1972 T850 also, so no telling what any one person might be talking about if they don't give any details at all.