I have a 97 Wrangler (automatic trans., 4.0 liter), completely stock except for 4 in. body lift and 32 in. tires. Vast majority of driving is on road. Any opinions on the best value in rear diff. lockers for my situation?

well if is has a D-35 rear differential I'd swap that out first.

How can I find out which diff. it has?

Google Dana 44 and Dana 35, both came in jeeps of that year. The Dana 44 is better. But don't get hooked on the coolaid. If all you are running is a 32" tire and thats all you are planning to run, just get an Aussie Locker. They are 200 bucks new, and the owner is a vendor on this board who stands behind his products. I've run a few myself personally and I can vouch for their quality and durability. If you are planning on running bigger tires, I would consider tracking down a Ford 8.8 rear axle from a 95+ explorer. Do some research and read up on it, the Dana 35 is considered inferior and too weak for pretty much any 33"+ tire.

please cut that body lift down to at least half. that much of a body lift puts way too much stress on your body mounting bolts. budget boost lifts [aka BBL] are spacers that go between the spring and the top of the coil bucket. they are just as cheap as body lifts are and still small enough that you wont need to worry about new track bars or adjustable anything. but you might get some vibration from the rear drive shaft. i did with mine, i put three washers between the frame and skid at all six bolt locations and got rid of the vibes. i have had great luck with aussie lockers. they are cheap, easy to install, and quiet. good luck.