Of course I have seen many period accessory brakes for small drum, but were there any for the large drum? Something like the Rocky Mtn type?
Yes Rocky Mountain did make accessory external brakes for the large drum. They are being reproduced but the most common complaint about the reproduced version is they do not hold in Reverse
So did AC.
Here's the Rocky Mtn. Improved car brake using the Ford large drum.
And the ACME brand too.
What everybody today calls "Rocky Mountain" brakes actually are a reproduction (with some minor alterations) of the AC brakes from the era for '26/'27 Ts. The actual Rocky Mountain version was a much better brake. In the RM ad posted by Dan T above, you can see the anchor point for the brake band slightly below center rear. Those would not have the braking in reverse issue the new brakes have. In the AC ad posted also by Dan T, you can see no rear anchor point, and the front bracket is a match for the new RM brakes.
Anyone have photos of period accessory large drum brakes like these on your T?