At the time, Ma Mopar was making motors (race HEMI's) with 600 HP max. Technology has come along way. People today run much bigger, higher HP/TQ motors, nitrous, turbos etc. A posi will not stand that kind of power.

I'm not saying it won't brake, but they're stronger than you think.
With the times the op stated, he doesn't have "600 hp" so I would put the trac-lok (four pinion type) in. "If" he ever brakes it, put the spool in.

Go w/ a spool.
If you're on slicks, ET Streets, or any other type of tire that has hardly any tread on it...IT DOESN'T MATTER WHAT TYPE OF DIFF. YOU HAVE when you're on wet pavement. You will spin out just as easily w/ a suregrip as you will with a spool. It's the tires that matter, not the diff.
I've logged a bunch of street miles w/ both suregrips and spools on both normal street tires and drag tires on wet and dry pavement. Unlike a lot of people who always chime in on this subject.
A good tight suregrip unit, whether it's a stock mopar unit, a locker, or whatever, will spin both tires equally on wet pavement just like a spool b/c you're on a slick surface.

The only thing I noticed different on the street is turning at really low speed takes a little more effort. Other than that, it drives just like anything else.
I've never experienced or even heard of the car wandering after letting off the gas at high speeds...unless you were on bias tires w/ too low of air pressure. Again, that'd be due to the tires and not the diff.