You will have to enlighten me on which year Ford switched to the 100mm metric 8 pattern. Otherwise, the lug pattern is the same on all 8-bolt wheels. 8 on 6 1/2, clear back into the 50's, I believe. I wasn't aware of the clearance issue on the calipers, but I know the GM wheels have a smaller hub pilot hole.
The only benefit I've ever seen, with 16.5's, is they used to be wider than a comparable 16. That is prety much moot, since there is such a variety of size vs aspect ratios, in the 16's.
Only one person I know, has bought 16.5's recently. He has large tires, on a lifted Chev. He liked the way that they look, with a slightly larger wheel, in the big tires. BUT, it's strictly a driver. He rarely, if ever pulls anything with it. At most, a car trailer, with a hobbystocker onboard.