Is there anyone in your family that would have had to register for the Draft. If so do a military search on any male in your fathers family and his address would be on the registration. Every man had to register.
My father served in WW1 and he had and did register for the draft in WW2 and he had lost a foot in WW1.. It might be after the census; but could be that he registered in 1940 or 41. You might hit the address right on the head. If you need assistance with the military search. Let me know.
You can do a general search on your grandfather and it will have his military history and what he registered for. Check your grandfather, uncles and don't rule out your sisters. Anyone who might have been living in the family at that time and would have had to register for the military. Women did serve in the arm Forces.
Look for any land grants or real estate dealings he (grandfather) had. He might have been in transition from one state or district to another. Maybe a job move also.
If you want help. Just provide as much info as you can. Name, Date or estimated date, Year for military is all that is needed; but month and date help out. Name of his (Grandfather) wife and children and state he might have been in. Don't give names of anyone who is alive. The only problem I have with the 1940 census is there is still a lot of people still alive who were born then and the 1940 census will show that.
Its up to you. If you do it yourself. Just go up to search and do a military search. In "keyword" put registered for WW2 Draft with a question mark behind it. Put in as much info as you can. You might find where someone has done a family tree on him (Father or grandfather) already and you might find info. Be sure and look under Public Trees. You never know who has done one. You might be surprised.
If you have any kind of idea where he might have lived (father, grandfather. Go to that City or state and check for a 1940 County census. The county in a lot of places did or had records of the census.
Then try the outfit in Utah. The Morman church. Thats where a lot of your information is generated on Census work. You might be surprised what you might find. If you have the slightest idea where anybody in the family went to highschool and was attending. You might try getting in touch with the elementary, high School, or college.
You might go to NARA.Com and try to find out about military records for any one in the family and try to get their service records. NARA has offices throughout the U. S. It might be onenear you.
If someone had a trade or profession. He might have belonged to an organization that is still in existance today and they might have records.
The most important thing. Go to your or call up your VA (Veterans Adminastration office) and try to get what military info (Grandfather or anyone who was old enough to serve.) you can from them. They are generally on the county level. Especially if you know that there was someone who definately served in the Armed forces. If he or she was a veteran. You are talking to a veteran and they will be more than happy to help you.
These records will get you to an address. It is according to how important the information is to you. Talk to whoever is around about schools, any old war stories. Anything they can tell you about the 1940's era.