...and perusing Craigslist, came across this:
http://albany.craigslist.org/wto/5889142387.html
37x13.5x20 Toyo MT's, about 5K on them, $600 for all four.
Other than the obvious penalty in mileage (should I expect to even be in double digits??), just HOW bad would my 5.3 bog without...