like always....it depends on goals now and future and what you are starting with, and what is readily available where you live. i would start with a few days doing a inventory of the local u pulls and pricing.
do you have a factory powertrain? do you plan a powertrain upgrade? what kind of tire size? if your going to need to regear anyway from stock ranger offerings and have to change wheels you have some cost effective potential options.
cheapest and easiest if your tire size is sane and your good with your factory gears if they are factory gears..especially since you do not want full width..plain and simple will be a d30 or 44 swap from a cherokee or wrangler. likely get matched gears to factory ranger ratio and cake to do and you can keep your current wheels..
if your lucky and full width d44 ford hi pinion that is fairly cheap or a pos ( and likely overpriced) low pinion eb axle is available local, those are no brainers. your getting lockouts.
but if your going that way your gonna need new wheels.
and if your gonna need wheels and dont have a workable set already and plan to narrow anyway finding cost effective options is fairly easy to do.
the chevies and dodges and fullsize jeeps thru the 80's had dana 44 and 10 bolts and are in mass over the 77-79 ford axles and usually real cheap complete and have decent brakes.
so swapping the diff to the driver side during the narrowing isnt a big deal at all.
the 90's isuzu rodeo and honda passport run a d44 out back with the chevy bolt pattern...the later models have disk brakes...430 and 456 gears with l/s are common.
other then that, a doubler setup that allows a passenger drop case and a 14 bolt and gm or dodge d 60 will allow some great options.
just remember....dana, new process, borg warner.....dont have to be pinned to one brand vehicle.
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