No, you can’t. For starters the F mount was originated in 1959. Second, and more important, mounting a pre-AI lens will actually damage the D50/70/100 bodies. 1977 and later AI lenses can be mounted but only CPU autofocus lenses will have TTL metering.
FWIW there are companies that will “chip” manual focus lenses so they will have functional metering.
FWIW I use a manual focus 85mm f2.0 AI on my D100 for portraits but it has no metering. A moot point since I use an incident flash meter anyway.
FWIW you can get an adapter to use Nikkor lenses on a Canon body. This combination was used for some technical reasons to shoot the stop motion film The Corpse Bride.
WonJohnSoup, I think it has become nearly useless to give specific advice on which DSLR to get. Nikon, Canon, Pentax, Olympus and Minolta all make exellent entry level DSLRs and you can’t go far wrong with any of them. I suggesgt you handle all candidate cameras and see which one feels right in your hands. Honestly I believe that good ergonomics are more important than the incremental technical differences in these cameras. If you like Nikon but the D70 costs too much consider the D50.