How much is a reasonable price to instal a Revtech differential drop kit ?

Like any repair on a 20 year old vehicle it's not possible to quote a price because of rust, wear & tear etc. Should there be no problems you would be looking at $125. for the kit install. Some thing's to consider before and during the work would be changing the angle instead of doing a full even drop (which it tough & expense unless your only dropping 1") would be the possibly of a vibration at road speed. The axle has a factory level and changing that can & normally will cause a strain on the front drive shaft from the transfer case, this can be corrected by having a drive-line shop install a pilot joint in the front of the shaft (I would try it then if the vibration is bad I'd would have that done). Another is the possibly that the ball joints are already damaged. If you've got a 100,000 miles or more they are due for replacement anyway and that's a good time to handle that problem, when a ball joint pull's out it normally will damage to front fender. Also take a look at the idler arms for wear and replace them if there's any movement, tires are just to pricey to wear out. A lot depends on the lift you have installed I would image it's at least 2 to 4 inch's to be damaging the CV boot's. The CV joint has a lot of angle play and normally the boot's install from the factory could handle 2" of drop. 20 years old boot's would not but the newer super boots can. If it's over 2" lift, dropping the axle is about your only choice.