Funny you ask about gas mileage...it will mostly be a wash. I used to think with the proper gears, OD and tire set-up that I would be seeing mid to upper teens... I was fooling myself. Again, my setup is 5.5" of SL, 1.5" BL, 35" MT MTZs, 4.86 gears, NV4500 (0.72 OD)...I get about 12 around town in what I would call "spirited" driving--others might call it aggressive driving. On our trip to the FL Keys last fall, we averaged about 13-13.5 for the 3K+ miles. There were some tanks where we were cruising, running upper 60s to lower 70s and saw 14 mpg. We had one tank at 15 mpg--cruising across the everglades with very few stops, lights, running 62-66 mph.
Recently--two weeks ago--I made a trip to BHM, AL (~500+ mi each way) running 75-80+ mph ont he Interstate and saw mileage from 12.5-13 mpg. If I run the back roads and smaller highways at 60, I think I would make the middle teen-mark. But, typically, I am looking to get from point A to B and while not necessarily in a hurry...its difficult to run less than 75 on most Interstates without being the "problem vehicle fouling up the flow"...inevitably you get cock-blocked behind a semi if you drive too conservative...so I find it more suitable to run in the upper 70s to about 80. I can take my hand(s) off the wheel and it tracks nice and straight.
But getting back to mileage and economy...these are BRONCOs...they are 4-5000 lb iron boxes-depending on trim (cages, tools, extras), oftentimes, jacked up in the air (like mine) damn near 3 ft; you cant expect it to get great fuel economy. As well, I run most of the time a safari top only. I dont seal my soft-top around the windows even when I do have them in...this all increases the drag. I would love to think that a Bronco modestly lifted (<=2.5"), hard-topped, EFI, OD-tranny, on smaller tires could easily see the mid to upper teens on 30s or 31s. I ran that way (minus the EFI and OD and hard top-seasonally) for years and saw 14 mpgs for similar highway trips (slightly lower speeds).
Ultimately, you should be thinking about performance and utility. What do you want (performance)? What do you need (utility)? What kind of driving will you most likely do? Configure around that.
I wanted to build something that I could drive a few hundred or a few thousand miles, get whereever it was that I wanted to see or do while I was there and then get back home. Cruising to Alaska and or Central or South America kind of trips. Colorado, Utah to wheel or going back home down south to the beach to surf or haul a couple of canoes to the Boundary Waters... Thats the beauty of the Bronco...it does all that with style.
The only reason I mention going a little larger in the axles...is that you will probably spend alot more of your time at lower highway speeds, so you dont need to and probably wouldnt really want to--and it wouldnt do so great anyway--70 mph @ 2000rpm. If your running 60 mph in the mountains, you will not be able to use your OD, cause it probably wont want to pull those grades at 1800 RPM. If you do run up to 80, its probably to pass or b/c you have to be somewhere--hence fuel economy may not be very relevant...so if you can find a ratio (4.33s) that gets you 80 at a little under/over 3K than thats probably pretty sweet. FYI, 2600 would put you at 71.5 mph (w/4.33s)...good power, not alot of gas, plenty of ass...just my opinion. If you think you will go with 33s down the road, definitely do the 4.56s. And remember you have to gear both axles roughly the same (4.88 vs 4.86 or 4.31 vs 4.33 or 4.54 vs 4.56), but I am sure you already know that. Expense-wise, its best to pick the right gear the first time...and anticipate growing pains.
As far as my cam, I am running a 2020 grind from Crane (PN 444211--actually its a 444212 which is the kit with cam and valve springs) for EFI controlled 5.0s. I am pretty happy with it.
Good luck. I am sorry to be so long-winded.