Travel is a good thing as you want to make sure the shock isn't going to over-extend itself, bottom out when the suspension compresses or just limit suspension travel overall.
I noticed in your profile you have a 2WD, do you plan on lifting it (Fabtech, RCD, etc) or putting on a long-travel suspension (Camburg)? If so you may want to hold off on shocks until you measure the front & rear of the truck for correct shock lengths or use the lift/long-travel kit's shocks.
Now if you are buying new shocks just to replace the stock crap ones I'd look on this page:
Note: I had to look under 2006 as they don't have any Rangers in their database under 2007, none the less same type of suspension and shocks.