I've been toying around with swapping the 4.56 rear end gears in my 1964 f250 with a Dana 60. I've located a Dana 60 axle out of a 77 f250 with 3.54 gears. I'm having some difficulty finding out exactly what would be involved in swapping the 3.54 gears into my housing. Can anyone give me some details on this? My second question is how these near gears would affect my trailer towing ability. THe truck has a 292 V8. Thanks

 

I am not too sure whether you have 4.56's now, and are considering 3.54's. If you have two D60's, one with 4.56's, and one with 3.54's, instead of changing the ring, and pinion, why not swap out the entire thing? Then you will not have to set up new gears.
If you must change the gears, and not swap the axles, a master re-build kit will be required. This will come with shims to set preload, and lash. New ring gear bolts would be a good idea too. If the bearings are in question, then a master overhual kit will be required. Then the old bearings will have to be removed, and the new ones pressed on. If this is your first time setting up gears, I would only recommend this with good supervision from someone that has expeirence with this. Getting something wrong here can be really bad, and do more damage, and cost more money than just having it done by a pro. in the first place.
If you have 4.56's and are going to 3.54's your 292 will struggle with towing a trailer. If you have 3.54's, and are going to 4.56's, the truck will not mind the trailer as much, but will wonder why the engine has to spin so hard when it is on the highway and empty. Depending on tire size, the engine might tach kinda high.