Protect your paint and scratch the bed. It's a truck.
And besides, these beds don't scratch much, and the scratches don't show as much as they do on a painted metal bed.
I was in COSTCO a couple of months ago, and there were two people at a table selling them. I asked how much for a Tacoma. "$500." I asked them what they cost at a dealership. "A thousand bucks."
A month later, I was in the dealership getting the brake line recall taken care of. I asked them...
I don't baby mine, but I've never spun a tire on acceleration.
Yotota is correct; using the rear locker around town is a poor idea. There's a reason differentials are there.
Well... here's the Fumoto plug I installed, so it has the thread size.
https://www.amazon.com/dp/B01HP5UZIO?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2