The auto has a really deep overdrive. .70: compared to .83:1 in the manual trucks.  So you can go with a lot more gear with an automatic and be ok on the freeway.  I'd say 5.29's with 35's, and 4.88's with 33's on a automatic truck to keep it in the powerband better.

Marlin has a speed and rpm calculator off his main page.  Plug in tire size, ratio, rpm and get speed.  Remember your overdrive is .70:1 here is the link link to marlin speed calculator

Stock gears are 4.10's with the automatic trucks (5spds get 3.91's) and I think it is under geared.  All the automatic Taco's I've driven have problems hunting between 3rd and 4th because the big overdrive puts the engine out of its narrow powerband.  Towing and driving on hills makes this worse and I'm always manually shifting it out of OD to keep it from hunting. Getting the revs up a bit won't hurt mpg and will help the power out a lot.  It's a Toyota so cruising at 2700rpm is no big deal at 75mph.  ~2700rpm = 75mph with 35's and 5.29s.  ~2500rom = 75mph with 35's and 4.88's.  I doubt the extra 200rpm will hurt mpg.  It might actually help with the extra drag of the lift and tires.

FWIW...  A 5 speed Taco with 3.91's is at 2650rpm at 75mph.  The 4runner with a 5speed has 4.10s as stock gears.  So with a stock 4runner 2800rpm is 75 mph.  So cruising at 2700rpm with your auto is no big deal.