To go with that a $$ comparison is in play... gears for either axle is $200 plus install almost anywhere you go, most axles can be had for around $200 or less at junkyards so considering gear install is at least $300 an axle if you take everything to a shop already pulled (more if in a rig) swapping axles is more economical for stock ratio's, you can sell your current axles on craigslist or whatnot to make a good chunk of that back as well...
As for where to get things, back in 2010 when I did my Ranger to 5.13:1 I bought the gears from TRS as Jim has or had the same price as anywhere else...
With what everyone else is saying, tire size makes a big difference on gear choice, so let us know that and we can recommend a gear ratio better, no matter what your truck has in it now. 3.73 and 30-31" tires is reasonable, some people like that up to 33's but that's more 4.10 territory...