Interesting find on the oil filter... I was trying to cross the number you listed, and found some interesting information. Could be nonsense, but it is on the internet! (see link)
The engine holds 6 quarts. It originally used single grade oil, as that was all that was available. The common substitute is 15w40 diesel oil. It is closer matched to the old flat tappet engines. The new gas engine oils are designed for roller cams and emission systems, neither of which applies.
The transmission holds 18 quarts. The plug by the shifter is the fill plug. All the cases are common fill, but the passages are small. The oil will need to go in very slowly, or it will dump in the clutch through the input shaft. The original oil was GL1 90 mineral oil. That can still be bought, but it will slow the hydraulics in cold weather. A common sub is the same 15w40 diesel oil.
The steering gear uses 90w, but few of them will hold oil. A common fix is to pump it full of grade 0 or 00 grease. It is a simi fluid grease that is thick enough to stay in, but not channel away from the gears.
The air cleaner, did you check the wire mesh in the canister above the oil cup? There is a mesh filter that is commonly forgotten. It needs to be cleaned, and if packed with dirt (most are) it will need to come out and be cleaned or replaced. Not easy, but necessary.
The alternator conversion, the bracket will most likely not fit. It will be a start,but will require some careful fabricating. Getting the alternator mounted straight, square and solid is essential. You will want to get a wide pulley to fit the belt. Don't use a narrow belt as it will bottom in the engine and water pump pulleys and slip. Follow the wiring directions carefully. If you get stuck, ask. We've been there many times.
How is the rest of the wiring? Unless it's been replaced expect it to be in bad shape just by the age.
Once you get it running, put it through the paces. Make a list of everything you find that needs attention. Unless it has had some work, expect to find problems. It's just the way 70 year old machines get. What you don't want is to take it apart, fix something, put it back and have to go back in!
Before you go any further, consider ordering a shop manual. It will more than pay for itself in mistakes not made! Get a paper copy, not a download. You want something you can carry to the shop, get dirty, write in it. Internet advise is good but questionable. Nothing better than having verifiable information in hand when you need it!
Have fun, ask all the questions you want! We want to help keep them out of the scrap yard!