Hi hgporter
It sounds like you may not want to use the router for this job BUT a 3" wide hand power planer or a 3" wide hand belt sander, that you can find in some pawn shops at the right price.
You should find many of the 3" power planers that should be in good shape because most people buy them and only use them a time or two on a door frame.
Now for the belt sander that's a long shot, you need to check them out well b/4 you put the bucks down on the counter for them, many people cook them or to say over work them but they can and do a good job with some 40grit paper on them they will rip tons of stock off quick some times to quick. (low spots) they do like to dig a bit.
For about 15.oo bucks,,,3" power planers
http://search.ebay.com/4-planer_W0QQ...ageNameZRC0024
Good LUck with your quest
Bj
