Ummm.....if memory serves, they call for a 4" and that's what I used. I think you're gonna have a pretty good gap if you use the 4.5", but if you can live with that, OK.

Rusty

They call for a 4" hole, but if you go to 4 1/8" it makes life alot easier to get it together and the hole will still be filled with the hitch.

I won't be bothered w/ at most a .5" gap from my saw. I've got enough crap laying around here to "fill" the gap from underneath. I might use some plastic, sheet metal, or something similar and make a plate and super glue/silicon it from underneath to fill the gap. Its a work truck in my mind and a little gap aint gonna bother me.

Just some quick notes to make it easier.

Remove spare tire.

Use a 4" x 4" or something similar across your bed rails to drop a rope from, through the hole in your bed and tied off to the hitch to hold it in place while you bolt it up.

Loosen the body mounts holding your bed in place, not remove just loosen. This will keep you from having to fight lining up the bolt holes.

Put the back of you truck up on ramps or something sturdy to give yourself plenty of room to situp under there. This is a pain laying on your back. IMO I don't trust jack stands or jacks. I have also had concrete blocks break out from under a truck so I stick with ramps myself.

Sorry I forgot to tell yall that I keep my spare in my bed (35's don't fit under the bed) and that with my lift and the tire gone, I can sit up and still have enough room to cough w/out hitting my head. Thanks for the advice.

P.S. We have also had concrete blocks break on us before, so now all we use them for (pieces now) is for tire chalks.

I got mine from http://www.hitchfinder.com for a decent price. I got the Reese bolt in package...that way you can switch between gooseneck or 5th wheel...not bad at all to put in... about 1 sixpack ought to do it...:D