Hi Pete
I have no answers regarding the dimensions of the outwale and cap, but can post images from a couple of the Old Town catalogs showing the IF model.
I know there have been posts about the IF model in the past, but the "search" function brings up too many non-relevant posts when looking for "Old Town IF"... like, everything Old Town.
The first image is from the 1901 Indian Old Town catalog. You may see (by inference) that the IF was the designation for a guide model canoe.
The second image is from the 1914 catalog. This is an interesting page, because it clearly shows the three grades of OT canoes.
Someone else who has more specific answers will eventually jump in. Bear in mind that there are fewer of the older Old Towns out there, and there may not be someone reading this board, at this time, who has one to measure... but if somebody knows of one, the word should get back to you.
Catalog images courtesy The Complete Old Town Canoe Campany Catalog Collection, 1901- 1993, available on CD from
http://www.wcha.org/catalog/ and
http://www.dragonflycanoe.com/cdrom.htm on the web.
Kathy