Just bought a LWRC Repr 20 inch barrel, have decided on Night Force, looking for opinions on 3.5-15 or 5.5-22.  I will be hunting deer, pigs, shooting paper, and have a huge field (1000+) to do it in.

I'd say go with the 5.5-22 if you think you'll be doing some long range shooting, but you might think that the 5.5x is a bit too high for the low end.

This is why I'm looking at the Bushnell HDMR 3.5-21x50. Great high end and low end magnificaiton.

Definitely 3.5-15.  That is more than enough to shoot 1000y/m with .308/7.62x51mm.  I'd go with the Nightforce F1 3.5-15x50, I think that first focal plane reticles are more or less required for mid-ranged to high-end variable powered optics this day and age.  Reticle choice would obviously be down to personal preference, but I'd go with a mil/mil system.

The larger field of view offered by the lower power scope will be much more useful against moving targets and also during low-light or night shooting if you have a clip on night sight.

I am looking at a Laure mount for this scope, it appears the popular one is the 104?  Is that the way you would go?

I've got a Leupold Mk. 4 3.5-10x40mm in an LT-104. Clears my Troy rear BUIS just fine.