I have this issue that slows me down when I think of getting a new bike. My arms. Fit. I was 6'1/2" and have been shrinking the past couple of decades but my inseam is unchanged and long. My reach, fingertip to fingertip is over 6'2" even after shortening my already narrow shoulder width a full inch with collarbone breaks. So to be comfortable on a bike, I need a really long reach despite my short torso. (With the classic elbow to seat nose, I need handlebars 4-5" past my long fingertips.)
Years ago I wrote a Fortran program that I could input the published geometry of a prospective frame and it would output the stem I needed and the weight balance between the wheels. (I was looking into a ti bike; having ridden a Merlin MTB 10 years before and having my eyes opened to "this is it! Just make it a road bike". The result? There were no stock frames out there that would give me optimal weight balance and good downhill handling and not require a custom stem. A $4000 class "B" fit? Nah.
Since then I have had two customs ti's built. Love the rides! Getting a new, much lighter, much faster, much sexier bike and having to settle for the "B" fit? Still, nah. I might resurrect that program and run it on the new stuff. Every once in a while a truly fitting bike comes along. My My 1976 Fuji Pro I raced. An early '80s Univega Competition with the same seat angle and top tube. (My first ti is patterned after it but with the BB kicked up for 175s.) The rest? I have used stems of 140, 150, 155, 175 and two of 180 cms.