That's an interesting combination of numbers. A798 suggests mid 1926, and given the proximity to my own body number I wouldn't be surprised if your car has 30x3.5 clincher tyres.
What stands out is the engine number is much earlier than it should be (about 200,000 earlier), suggesting it isn't original. This is not unusual of course; a lot of T's have had parts of random years installed and there are plenty of T's out there with non original engines.
Can you tell us, 1)how many dips the pan has under the engine; 3 or 4?,
2)if there are two bolt holes right at the back of the cylinder head, adjacent to the magneto post?
And to further work out what the situation is,
3)are the brake and high/low pedals wider than the reverse?
4)is the brake drum inside the transmission wider than the low and reverse drums, or are all three the same size?
5)are there two bolt holes on the top of the transmission cover up against the back of the cylinder head and do they have bolts in them?
From this we can ascertain if the whole powerplant is pre 26 or just the cylinder block.