After seeing the pictures, it's definitely NOT a F40, and why it is important to post a few pics. No harm, no foul.
AGCO does have online parts manual(s) for a 40, and a model 40B. Looks like the 40B was the later version and most commonly used with a backhoe.
This is for the 40:
https://parts.agcocorp.com/us/en/apbsearch?q=masseyferguson/651282/l&c=00-00&name=MF 40 TRACTOR
This is for the 40B:
https://parts.agcocorp.com/us/en/apbsearch?q=masseyferguson/651383/l&name=MF 40B TRACTOR
For what it's worth, here is a link to TractorData on the 40:
TractorData.com Massey Ferguson 40 industrial tractor information. Bad thing is, it does not show the year by serial number.
This link is for the 40B and if you scroll down towards the bottom, it does list model year by serial number.
TractorData.com Massey Ferguson 40 industrial tractor information
So the key now is with the 40B TractorData showing the SN's. If not in that group, you have a Model 40. The important thing is now with the SN you know what manual to get as far as operator, or service. The parts manual can be accessed online at least for now. Case/IH revamped their online parts catalogs and show, but removed part numbers for things they do not stock anymore. But was very handy when you needed a certain part such as an axle housing, etc. you could copy and paste the number and search salvage yards that way. I now have hard copy parts manuals for most of my older tractors to do that.
Now that you can determine exactly what you have by serial number, you can find a part you may need by using that online manual. Use the part number listed so you can find the exact part you need. I did another quick look and on the 40 there were different power steering pumps used on them through the production of them. And listed is the serial number break where they were changed, and states "up to xxxxx"
And you can also find the manuals you need, either by the 40 or 40B. Personally Google gets the best results when I'm looking for a manual. Most will be sites that make reprints. But my go to place is Ebay. There you will find mostly reprints, but occasionally you'll find OEM manuals, and conditions will vary on them. Most generally there they will have some smudges from being used, or tattered corners of pages. What I get are plenty good enough for me, and I'll probably add a few more smudges along the way when working on something.
Hopefully this will get you back on the correct path to find what you're looking for. And please remember when posting about something include pictures if possible. Photos can speak volumes in themselves. I knew as soon as I saw the dash and front end, it was from a 60's era tractor.