Re: 3.55 axle ratio and towing
Going from 3.55 to 3.73 won't make much of a difference. If you're going to spend the cash on a gear swap, I'd advise going to a 4.10 ratio, especially if you plan to regularly with it. Highway mileage will drop as the highway rpms will be higher, but you'll be able to tow the maximum amount possible for your year and engine with 4.10 gears. Stepping up to a larger gear doesn't mean your towing capacity increases, as the transmission, chassis and suspension can only handle to much weight before parts begin to stress, and fail.
Lower gears allows easier starting, especially when pulling trailers. One benefit is you'll notice less gear hunting when climbing hills. Higher engine speed means less downshifting, which comes in handy when towing a load.
Don't rule out tires either. Depending on the weight of the trailer, cargo and passengers in the vehicle, you can run smaller diameter tires which will give better performance. If you run 32" tires, stock, running 30" XL rated tires (provided they fit on rim, etc) will allow the feeling of you having 3.73 gears.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!