Do plan on custom made or off the rack?
If custom made then they will ask for several different measurements, waist(where your chaps will sit) upper thigh , lower thigh(just above the knee) calf, inseam, outseam, and the drop(crotch).
You seem tall, I would guess that customs would be the best, for a flattering fit.... I am tall as well, I have tried to buy chinks off the rack and they look ridiculous on me(too short)....I would go custom, if you get something timeless, not trendy, you will get your moneys worth!
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.