while not adding any horsepower.. you will probably find the OD transmission to extract some "performance" out of the existing engine.
Unless you live in a very flat place... the 26 is too big for a 74" engine..at least my opinion.
It worked ok in my hilly country... but it will need a 84" engine for fun
I find the low ratio OD and a 25tooth near perfect for my country (and the 84" engine). Shifting is easy, and you can really accellerate out of the curves...lot's of fun.. Seems like a much faster machine then..
I shift to 4th gear at 55-60mph for highway cruising..but the engine is flexible enough to do 45-50mph in 4th.
But I shift down to keep the engine running happy (and no lugging).
I found the rpm to be ok at 75-80mph with the low ratio OD.. but you should consider the high ratio version for 80mph constant.
The max speed limit is 62mph here.. and the first 3 gears see a lot of use. Even on some of the main roads over the mountains, first gear have to be used to get through some of the hairpin curves:)
I have killed lots of transmission gears.. even 2nd gear in the OD box (manufacturing problem I think, replaced on warranty).. I blame some of this on the 26 tooth I had on the original box. The 84" makes a lot of torque and the repro/ orginal gears was not up to the task.
Still, with the rpm drop I have had problems with "external" oiling.
The return pump seems to suck out the oil rapidly, but then loose the prime. This will cause the oil level in the crankcase to rise a bit... and some of this oil exits the breather line. I have the scraper installed.. and while it works fine when it works.. I think the 90degree oil line fitting has a too large ID, and is mounted to far to the right. I have now soldered in a smaller id tube into this fitting, and this now sucks oil from the bottom of the crankcase. The tube extends into the crankcase.. maybe 1-1 1/2 "
So far it looks like this tube have reduced the "lost prime" issue.. the return pump keeps on pumping(or squirting ) oil constantly.
Still, some oil mist exits the breather line.. but I have near solved this problem with a vertical tube and som trick plumbing.
Anyway... I need a season or so to check it out.. too much theory and not enough real-life testing..