Now that's restrictive. I think I'd take advantage of that pole. It's
almost a quarter wave on 20 meters. A half wave vertical, isn't dependant
on ground radials. I think an r-8 doesn't need to be guied. If not, maybe
an r-7. You might have to sacrafice 80 and 160, because it'll be hard to
put up more than one antenna. Best of luck!!!