I had the CL350 version of your CB. My brother had the 1971 CB version. Both were capable of over over 100 MPH (his a little more), and all-day freeway touring BEFORE the speed limit dropped to 55 MPH here. They also last about 25k-35k miles with good oils before a top-end overhaul and new clutch is needed. Tough bikes!
The CB175 is the design that became the CB750 SOHC engine. Same volumetrics, timing, cam, all of it! You can run those bikes WFO all day long and they will not even break a sweat. Once in 1972 I rode across South Dakota (westbound) on my 750 and met a fellow on a CB175 in eastern SD who was going the same way I was. I rode 90-100 MPH, he said he was running WFO at 80-86 MPH and he had more load on his bike than I had on mine, by a stretch! I camped at 6 PM in Wall, and about 2 hours later, here comes the 175: he camped with us. On the way back a week later, I met him again: he was still traveling the same overloaded way, flat-out all the way, but going almost 90 MPH because of the westerly tailwind. Indestructible, those bikes...