I like your approach of PN 75109 (1-3/4"), it may be easier to fit than the 1-7/8" and run pretty well depending on your application. I don't know however, as my experience is with 1-7/8".
I recommend you consider future availability of whatever PN you choose as you are pretty much making a commitment due to the cutting required. Definitely order the "Jet-Hot" type coating inside and out; it is good. I actually bought mine uncoated and shipped them to Jet-Hot back in the 1980's. While their run time has been somewhat limited, they are holding up well. Don't overheat them on motor startup due to timing not yet being adjusted. The coating doesn't like that.
I have a backup set of PN 75110 and a new W2 2" PN for future use, neither of which I have yet to fit or run. I am committed! Of course, if you have access to someone who can replicate, the concern is not there. Just some thoughts to consider.