I will admit my 75 has never been driven on the ice. I will also admit that my 93 is so tight that its a handful in any kind of ice/wet roads, especially since the bigger injectors went in. My driving experience between my 93 ls and detroit locker in full size trucks I would not have a problem having a detroit in the rear of any of my trucks. In fact all my trucks except the 93 will eventually have detroits in them. There are only two reasons I won't have one in my 93. One is towing, the other is the ls works perfect in the truck, no reason to change it out. I have driven my dads 95 dodge with a supposed ls and it spins one tire around corners. Get on my truck on dry pavement and you better be ready to countersteer, cause the rear ends comming around.
My wife and my brother will not drive my 93 in the rain because the ls is so tight and the cummins will get you in trouble in a heartbeat. The truck will get loose on wet pavement in every gear except overdrive quite easily. Work at it and it will light the tires in 5th on wet pavement. I like my ls this way, I hate having one wheel just set there looking stoopid while the other one spins. Thats why all my other trucks will get lockers for offroading and truck pulling.
My buddy has a 78 ford bronco on 38" swampers that until recently was his daily driver. Had half ton axels in it with lockers, truck was great, except for breakage. He stepped up to one ton axels and locker in the rear, but just ls up front. First time on the ice he hated the ls up front. Went to detroit up front and like it alot better. He said the truck needed ALOT more input from the steering wheel on crappy roads with the ls in 4X4. Just his opinion.
I apolojize for my long winded ness. Many people do have different opionions on lockers, but they usually have them in something small, short wheel base, tall, large bias ply tires. This type of vehicle just makes the locker have a larger effect on handling. With our large trucks a lot if soaked up because it is harder for the truck to be tweaked like a jeep. I on the other hand prefer as many wheels as possible pulling the truck, wether it be on a sunny day, or crappy as heck. I am a driver though, not just a run of the mill, gotta have ABS, airbags, and all season radials to get anywhere. Not trying to cause an argument, just letting everyone know who I am. I live by differnt strokes for differnt folks. Some people want something thats easy to drive, and thats fine. For a majority of the population that is adequete. For me though, I don't mind my stuff a little "squirrly. " I have driven my truck long enough to know what is going to happen before I move the truck. The lockers, or ls seem to always have the same respnonse to wet roads, excess throttle input, and ect.
I would not sweat a locker in the rear of a full size truck, unless towing heavy. 7,000-8,000# I don't know. With responsible driving you should be ok. If you're gonna be torqueing the crap out of it, don't be suprised by a broken axel. The tire wear, I like the fact that the rear tires tend to wear at the same rate on my trucks. We used to have a dakota with an open rear, and it would always chew off one tire. I dislike that. I dislike standing on the gas(or diesel) and waste all that performance on one tire smoking. My friends and I have little problems with a detroit, or even a lock right for that matter breaking. Its usually axels shafts and u-joints. A cheaper way to decide if you want a locker or not is to purchase a lockrite, it replaces all the gears in the differetial carrier. Easy install in a couple of hours. No special oil, no ratcheting noise, and locker performance. I run one of these in the front of my 75. Haven't had any problems yet. I truck pull it with sometimes 1000# of suitcase weights on the front bumper, BUT I am always going straight while doing this.
NOW in conclusion. When installing a tight ls or a locker be prepared for the driving to be differnt. It will have a noticable feel, locker will be more pronounced. You will start having some issues with axel wrap when on the power hard, because our trucks have leaf springs and blocks. You will now notice this because you are no longer spinning one tire. If you like the feel of planting the tires to the ground, prepared to be able to steer the truck with the rear end, and in general like to drive something performance oriented then go ahead and get the ls or a locker. If you are unsure, your truck works adequetly for you now and dont mind being stuck on a patch of ice with the other tire on dry pavement then don't change your truck. If you want, just come on out to Iowa and drive all my trucks to see if you like em!! I hope this helps.
Michael
Attention: TDR Forum Junkies 
- and would like to upgrade to a limited slip, but the PowerLok unit is too #@!$% expensive. 
Issues while towing are my biggest concern, and it sounds like a locker may be too aggressive for what I'll be doing. 
