Think the F3 have some special flash hotshoe, which is not compatible with the mainstream nikon flashes unless you get an adaptor (experts please correct me!)
Also, the kit lens with the D70 might not be fully usable throughout it's entire zoom range on the F3 as its a DX lens, and whats more, its also a G lens, so you can forget about setting aperture on the F3 with the G lens.
And if the lens are AI/AIS, you can't meter with them on the D70.
If you are budget conscious, it makes more sense to stick with the F3 then paying for a new D70. Unless of course you die die want to go digital, in which case, can you give me the F3?