Yes, it looks like a TO30 with the wrong color and decals.
You can buy an aftermarket gas tank and radiator from this site.
If the factory radiator is salvageable, try to save it. It is a better radiator and will fit better. You will have to find a used fan shroud or fab one up, it won't come on the radiator.
The battery tray, I don't know of a source for a new one, and at that age finding a good used one will be a challenge. If there is enough left of the old one, use it for a pattern and fab one.
Gas in the oil is common. It can get in from a flooding carb left with the fuel valve open. It can also get in from a rich running engine, or misfiring cylinder, a cold running engine, lots of cold starts without an up to temp run. There is a wire mesh inside the air cleaner. Good bet it is seriously clogged.
Be a good idea to crack the trans/mid/rear gear case plugs, see if water is in the cases. easier to get it out before it gets emulsified into the oil. Don't try to remove the big square cover, it's not a cover, that's the bottom of the hydraulic pump.
If you can easily get it running again, put it back together and give it a shake down run, put it through the motions, put an attachment on if you have one, make a list of everything you find wrong.
What you don't want is to go in for a major repair, put it all back together, paint it up real pretty... Then have to take it back apart. :(
A shop manual will be a good investment, you can get them on this site or Ebay. It will more than pay for itself in mistakes not made!
Let us know how it goes. Don't be afraid to ask all the questions you want!