[aardvarcus]

Thank you for your thoughtful reply.

My plan for the bumper is not to go any lower than where the stock one is right now, so not really an air dam to the ground type bumper, just a smoother flowing one. I still need to maintain decent ground clearance. My thoughts on the bumper are just to smoothly direct the air flow above, beside, and under the truck. Right now my front in has huge panel gaps(1/2" min to 2"+, no joke) that can't be aerodynamic at all. The front is way too open, the truck needs less.
My Belly Pan would be mounted at the height of the lowest cross member, which is 1.5" below the frame. That way I don't give up ground clearance, my lowest point is still the lowest point; just now that height is everywhere.

I had thought the Duramaxes were on thermal fan clutches, but I will certainly look into that. That would probably be a better idea than an E fan if I can find something that will work. Might have to modify something, a clutch is a clutch. I am going to get my programmer to engage the electric pin, so I can wire that up to run a clutch.

I want to get air on the truck for other reasons as well, once I get the bed cover I will probably pull the trigger on that. It is just nice to have.

Yeah, the Allison is basically the only reason I relented and got an automatic, I have heard they are bulletproof. Mine is an older one, and after I put the correct Dextron 3 fluid in it (Transynd) it really shifts nice and smooth. Previous owner must have put Dex 6 or some cheap Dex 3 in it, because it was clean and working, but it just wasn't shifting right. I hope no long term damage was done.

Yeah, I had thought about the gear swap and it just slipped my mind when I typed this up. I think right now I have 3.73 or 4.10 in it, but first gear on the Ally is so low I could go a lot lower no problem. If I had to do an extreme task there is always 4-Lo.