You can use any good quality oil and filter on the 3.9, just change it on a regular normal schedule. The 3.9 is a very durable and reliable engine. The 3.9 is an old school cast-iron block and it will run forever as long as you take good care of it. I am old school too and I change my oil at 3,000 miles or 6 months, whichever happens first.
Right now I am using Kendall GT-1 Syn Blend 10W30 with a Carquest Red Label (made by Wix) in my truck right now. I normally use Quaker State conventional 10W30 and a Purolator Classic filter, but at my last oil change I just wanted to try a different oil, and I had the filter left over from a Carquest sale a few years ago. I have heard and read a lot of good things about the GT-1 with liquid titanium.
My engine runs great on either oil, it might burn maybe half a cup of oil every 2,500 miles with the QS. I have about 1,600 miles on the Kendall and have not burned a drop yet. Kendall seems to be a great oil but it was expensive, IIRC it was over $5.00/quart. The QS in my stash cost me $2.16/quart at one of the sales they had at AAP a couple of years ago.
I have also used Valvoline conventional, and have used Napa and Carquest store brand oil with either Napa Proselect or the CQ Red filters. I did one run of PYB 10W30 and I used Maxlife for a couple of OCI's back around 70,000 miles. Out of all the oils I have used in my truck the only one I had problems with was Maxlife. It is blended at the thicker end of its given viscosity and as a result I took a slight hit on gas mileage and lost a bit of power on the butt dyno. When I am done with the GT-1 I will switch back to QS and use up my stash.