I'd lean towards pear rather than apple.

eciton...look up Callery pear and see if the fruit on your tree resembles that. If it does resemble it even a bit...it's a pear and Liberty won't graft to it.
Plant a apple seed and grow a seedling, then graft your Liberty to that.

Appears to be Callery pear. Graft a fireblight resistant pear such as Orient, Ayers, or Moonglow.

We do have an ornamental pear as well that was here when we moved it and the leaves look similar but not exactly the same, that's why I was assuming crab? Good to know it's also a pear,

It's about 6-8" diameter. Can I lop the top off 4' up and bark graft some asian pear to it? Should I leave any branches on? I have learned from posts here that persimmons and apples can be lopped off and peaches will die from it....so pears? Thanks!

Appears to be Callery pear. Graft a fireblight resistant pear such as Orient, Ayers, or Moonglow.

An even better idea.

eciton: Read up on top working pear trees. I'm sure there are some good youtube videos on it.

Should I leave any branches on? I have learned from posts here that persimmons and apples can be lopped off and peaches will die from it....so pears? Thanks

Most grafting I've seen done (and I've seen a lot via youtube and the like) have always left at least one nurse limb...including apples and peaches. I've only seen 1 time where a grafter (a professional) just "lopped the top off" to graft. You could do it no doubt, but if the graft were to fail for whatever reason you may well be SOL...that's why they try to have the nurse limb.