I have done literately over a 1000 gear set ups over the past 38 years and have never used any pinion depth tool or payed any attention to any pinion depth numbers. Start with the shim off the gears you are taking out and check the pattern and go from there.
The only guy I ever knew that could do that was John Giovannini, at Gevo's Gears and Rears. BigChief if you are in that league I take my hat off to you. I am not. I need all the tools I have and then it takes me a LOT of time to get it right. Interpreting the gear tooth pattern is another dying skill but is absolutely necessary to get it right. Most people can not do it without extensive experience.
That said , I do not know the skill level of the OP, but if he is asking about a pinion depth spec, then I can only assume he has never done a rear before.
"Start with the shim off the gears you are taking out"- exactly. I have found to need no more than a thousandths or two different from the original factory shim. But sometimes the shim has been chewed up so bad you need to start with an actual measurement with the depth tool.
As for a daily driver, limited slip is not absolutely necessary, but is desirable. We had a 1968 Buick LaSabre, a daily driver, I upgraded to a posi carrier [from Gevo] and it came in handy quite a few times. Mostly on slippery roads, snow, wet leaves, that kind of thing.
One more thing. If you are just changing the carrier from a non-posi to a posi, you can leave the pinion gear alone. Just swap the ring gear to the new carrier, and go from there. Do a contact pattern test first and try to get that same pattern on the gears again. Of course if you are changing the ratio, then you must start from scratch.
