IMHO, you'll be unhappy on that particular bike (unless you CLING to that notion of 60 mpg vs 30).
My mother had one (also an '85 500) and it, indeed, was very cramped. I'm 5-9, 225, and the cruiser bar on it put my elbows right in my ribs. And, twisting the throttle was a motion like turning a screwdriver rather than turning a throttle. Kinda awkward.
And, unless you have a largish Plexiglas-type windshield on it, you'll be fighting that windblast something fierce. Your neck, shoulders and lower back will really be feeling it after a week of that. On the other hand, if it DOES have a windshield, it might be fairly nice. The wind actually circles up around and pushes you ever so slightly from the back. At least, the handful of bikes I've ridden with such a windshield all did.
Bottom line, IMHO - if it has a windshield and the bars are OK for you, go for it. If not, keep looking for something a bit less cruiser-ish.
Good luck, either way.
Kirk