I would actually like to run an 80 front if I can, but I would need to sell my 40 axles first and I'm not sure I'll find someone willing to pay what I have into them for parts in a timely manner. But we'll see. And no, I don't expect nor would I want to do 81 in a 40 with a 2F on 37s... lol. Just comparing gearing.
40's drive pretty well at speed with a stretched wheelbase, even a few inches makes a big difference.
I ran an NV4500, toybox, splitcase for a while and the compound low was great. I was around 156:1. Didn't use it much, but it was nice for some stuff.