The short ribs between the full-sized ribs are known as half-ribs.
If a rub rail was factory-installed, the build record should reflect that, but it could have been added either by a dealer or by a previous owner -- a camp might have added rub rails.
Outside stems are wooden stems outside the canvas, but inside the brass bang strip, usually varnished, as on my fully restored 1922 OT Ideal (click on the photos):
but sometimes painted, as on my 1931 OT 50 pounder when I bought it:
Floor racks (sometimes called floor boards) are an accessory that can protect the bottom of the canoe from gear and other loads, and can keep
things drier than if loaded right into the canoe:
As to the interior varnish, if it is badly UV and otherwise damaged, it would have to be removed before revarnishing.
Though varnish can be removed with heat and scraping, the best way is to strip the old varnish entirely, usually using a chemical stripper. But to do that efficiently and effectively, the canvas should come off. The canvas (kor fiberglass) on this canoe may need replacement anyway, in which case, the time to strip the interior is when the hull cover has been removed. I suppose soda or walnut shell blasting might work, but I would be doubtful -- cedar (your canoe most probably has eastern white cedar ribs and western red cedar planking) is a very soft wood, and it is difficult to sand or otherwise abrade paint or varnish from it without also removing some of the wood -- and there isn't much wood in a canoe to remove.
Without seeing your canoe, or some good photos, it is hard to say whether you have canvas or fiberglass
Some pictures would help -- both to evaluate the canvas, and to decipher the serial number. (see the tutorial at
http://forums.wcha.org/knowledgebase/Tutorials:Posting+Photos+to+the+WCHA+Forums?do=comments ).
Looking at the serial number with a raking light (from a flashlight) sometimes helps. But be careful about trying to remove paint or varnish -- it is really easy to remove the serial number.
Greg