Hey Bill QQ - my 1450 was a 1978 production unit, had the updated steering wheel with the silver IH emblem center cap, 1" front axle spindles, cast aluminum lower grill housing, aluminum rear axle carriers, hood support with rubber blocks (used later on the seat trays) instead of the thin slotted rubber cover (this was a nice design change), internal wet brakes (same as earlier rearends) and maybe some other things I don't recall right now (I already mentioned a couple tidbits here that aren't often known about the later QL's).
My K321AQS ran that QA42A thrower like a beast. It had just the right amount of power to allow for completely variable hydro control you needed due to snow variations. I did go completely thru the thrower before I ever used it so I know that helped as well. I never had those fingers on the chute but didn't seem to need them. Early in my learing how to use the thrower I remember figuring out that to avoid chute clogging I needed to run faster, especially if the snow was like slush. It might not throw it that far but it got it out of the way.
I had absolutely no problems with the electric PTO when I was using the thrower. I will say that thrower is scary if you're in front of it with the PTO engaged. I know you have to look at it sometimes but that auger is dangerous so lets all be really careful out there.
Now, about the muffler - I never did change mine althought I considered it, especially when I had to change the air duct (Charlie recently posted a pic of it) because it cracked, and the tin muffler box panels rattled all over. At that time the dealer told me it wouldn't make any difference - my muffler was fine. I do know IH used 3 different versions on the QL. The early one had a stubby exhaust pipe that did not exit the grill. IH changed this and went to about a 4-5 in exhaust pipe so the exhaust wouldn't blacken the inside of the white grill housing. That one blew leaves and grass all over the place and if you used a thrower it would cause the chute to get hot and melt the snow causing clogs - so IH finally went to a mid length exhaust pipe (about 3") that just existed the grill by about 1" and was about even with the grill housing - that's what I had and worked perfect for me.
My only real complaint about the QL units ain't really with IH, it's with Kohler for using that dang whinny starter, which definitely isn't as quick as the old S/G.
Scott N - you're just sitting with your feet in one place for to long if'n you're gettin tingly-toes.
(And it's not fair to compare a twin against a single - that's comparing old iron to new).