I'm 6'3. Inseam on pants is 34" but if I remember I think I'm closer to a 32" inseam. If it even matters.
Will it be close enough I should I even bother going to look at it?
I'd say, make sure you sit on some 60/61/62cm frames as well so you can compare. A lot of factors come into play - arm length, torso length, leg length, preference, etc... . And not all frames labeled 58cm or whatever number have the exact same geometry and characteristics of others.
I'm about your height (more towards the 6'4" end of things) and own a 58cm road bike (Allez) and a 64cm endurance road bike (Roubaix). I also ride nothing by size XL mountain bikes. The 58cm is actually my son's who is 6'1" and it fits him like a glove. If I ride it, I have to use a really long stem, get the bars higher (due to such a short headtube) and raise the seatpost and slam the saddle back to make it work. The 64cm frame fits me like a glove for a tall man with a gigantic headtube and gets my saddle/pedal relationship perfect which makes the bike handle really well due to the balance. On a smaller frame, jamming the saddle high and all the way back puts a lot of weight on the rear wheel and it doesn't handle quite as well.
Examples with both bikes set up for me to ride...
58cm...
https://flic.kr/p/7305517620
https://www.flickr.com/people/[email protected]/
I feel like a moose on that bike as I really dwarf it.
64cm...
https://flic.kr/p/13316381455
https://www.flickr.com/people/[email protected]/
This one has all day comfort written all over it and, as you can see, I prefer a much more relaxed
French Fit with this bike (bars barely even or slightly below saddle) and the super long headtube. I used it in one cyclocross race last fall where it was fine and do a lot of gravel and pavement with it as well.
Bottom line - try a few things out. I prefer the stability and handling of a larger bike as the smaller 58cm bikes are twitchy, flexy/flimsy, and require some plumbing adjustments to
make them work for me. The bigger frames really remove all of that and fit like a glove right out of the box.
Again - it depends on your preferences, experience, and measurements. The bike industry is not kind to riders that are 6'3" and over. In that tall group, you will find way too many riding a bike that is really too small for them.