My 25 touring came with a 26 engine and a 4 dip pan and a 25 transmission. I understand the 4 dip pans are not as strong in the area where the transmission and engine mate up if you are using a 25 or earlier hogs head due to not being able to bolt the 25 hogs head to the block. I have a 26 hogs head which would mean swapping the transmission (or could I just replace the brake drum) but I don't have a 3 dip pan so either way looks like more money!!!
Why not just use what you have? It should be just fine. Four dip pans came in 1923 or 1924.
Use the reinforcement brackets for some extra insurance.
The 26-27 trans with the larger brake drum, 26-27 hogs head with mounting ears and upper support brackets, 4 dip oilpan, and wider clutch and brake pedals are superior to the older style. Upgrade.