will a gm 14 bolt diff bolt up to were a gm 10 bolt did without modifiction to the drive shaft and transfercase?

Probably. I'm assuming that the truck is lifted at least 3 inches.

The spring mounts may be different, but the driveline should bolt right up.

Use the original driveline on the new axle and there shouldn't be any problems with t-case fitment.

Also, there exists a wealth of driveline variations available for you as the need arises. You can retain the original slip yoke and change drivelines by purchasing the appropriate U-joints for the new combination.

Axles are generally very easy to replace, so I wouldn't be afraid to go ahead and give it a shot. Shouldn't take more than a couple hours to know whether or not it'll be a direct fit and figure out what, if any, mods will be required.

One thing to keep in mind, the rear brakes for a full floater axle are different than those on a semi floater. You may need to replace your master cylinder in order to restore proper braking.

Clay

If you use a 3/4 ton one the perches will be the same, but they all have 8 lug wheels as opposed to the 6 you have now. Also you'll need a conversion u-joint.

I know in the early 90s at least, there were some light duty 3/4 tons with 6 lug 14 bolts. If you can get one of those, that is the ticket if you already got nice wheels. From what I hear, these too should be a direct bolt in.

You shouldn't use the conversion ujoint if possible, they dont work as well, just get a new, bigger driveshaft made. If you have the need for 14 bolt rear you will be happier with a bigger dshaft.
Obviously, rims will need to be different. You might have to modify brake lines and like they said, you might have to move spring pads depending on what the 14bolt came out of.