The standard spec includes a spark arrestor to meet US Forestry regs---but I guess they meant leaves etc being caught up under the low level exhaust system and catching fire there. Otherwise known as the patented Triumph system to make you go like hell so that the velocity puts the fire out!
In answer to your Jackpine question, that is a common moniker for the 66 T100C, so the exhaust referred to would just be the stock siamesed high pipe for that year.
Which doesn't work as stock on the TR5T, due to the close proximity of the downtube to exhaust port. They must have altered it to fit, or just never mounted it (maybe why you didn't see a picture?).
I'm surprised a Michigander isn't familiar with that term for that bike, Bill Baird was probably responsible for it being called as such. Though I don't know if it was ever an "official" designation, probably just a popularized magazine dubbing.
I've been referring to the 66 T100C as a Jackpine since, well, 66.
I grew up riding Poker Runs and Enduros and spent many years riding in the woods up by M 61 in Gladwin. I did not know if it was a official model or if they had put together something special for the race. I did some web searches and it looks like it was a unofficial nick name for the early T100C. Jeff
Continuing the topic drift for one more post, in looking at the 1966 Triumph USA sales brochure, it does refer to the T100C as "the famous Jack Pine" model.
Don't know if that makes it "official" or not, or if it would apply to other years? But it certainly does to the 66.
OK, back to twisty pipes... I have looked at one bike with the 66 exhaust, but the right side was altered to fit, something was changed with spigots, and the engine had to be removed to mount the pipe. Musta really wanted that look...