is the 1970 f100 front drum brake spindle the same as the ones used on a 74 EB drum d44??????

yes

No they use a different type of seal where the inner axle meets the spindle. someone on the board probably has the spindle you need lying around. the f100 uses the same spindle as a dana 30 equiped EB I have some somewhere but they are probably all rusty from 8 or 9 years sitting in a shed.

can you just use the seal for the F100?? What's different about the seal?

The 74 should have the larger diameter sheet metal slinger on the axle shaft that a ruber lip seal slips over. The lip seal seals to the back of the typical dana 44 spindle. The '70 should use the spindle that has the seal pressed into the back of it. The outer axle shaft for this seal design uses a smaller diameter sheet metal slinger. This assumes that the f100 has the dana 44 with the kingpin open knuckles like every 70 f100 4x4 I have seen. Some people still dispute the fact that these axles exist.