I can see running 8" of lift for 42s, I agree. (That's a sweet looking truck by the way!) But, the OP said 37s and to me, that's way too much lift for 37's. I've not owned a Ford (other than a 69 Bronco I used to have) but, on my 87 GMC Jimmy (hence my screen name) I ran a 3" lift and 37s and on my current 2012 Power Wagon I plan to run 3" and 37s again. (it's actually not but about an inch of lift on the Power Wagon since it sits about 2" taller than a standard 2500 but, whatever- for simplicity's sake I'll just say 3" lift) I had contemplated a taller lift (6" over a standard 2500 so, about 4" on my Power Wagon) since it drags belly a LOT but, since I want to be able to easily load and unload things from the bed, it is my DD, and I value having a low center of gravity, 3"is the way I'll likely go. If I could get lower gearing for my rear axle (4.56 is the Power Wagon's ratio and is the lowest currently available) I might would contemplate stepping up to the 6" lift and some 40s but, if I am sticking with 37s, the lower lift is the way to go, IMO. Plus, as I mentioned I feel the truck works better at a lower height in terms of loading and unloading, it is my DD, and I like a lower center of gravity so, given all those factors, even if the lower gearing were available, I would likely still stick to 3" lift and 37s.
Yes, I realize a Power Wagon and a Jimmy are neither one of them at all like an F-350 but, the point of my post is that if I was planning to run 37s, I would not run an 8" lift, I would run something lower.