I have no reason to stick to a 3000m OCI when the oil is clean, the pressure is good, and there are no other indicators of problems.
Right now we have 5500 miles on QS conventional in the Durango. It's still amber and clear like beer. I expect to change that truck at 7500-8000. Want to break it in on synthetic so MCSB will be on tap as soon as I find it in 5W30. 5W20 seems to be the norm for that brand, at least at WM. I'll check in at AutoZone and a few other chains and see who has more weights in MCSB.
The Torino needs dino, it's too old to take advantage of synthetic IMHO. When I drop in an EFI 302 later on, I'll be happy to feed it MCSB at least, if not a full synthetic. the 351M engine is low compression, oil burning, and not worth putting anything premium in it. SuperTech, here I come, with BELLS on. If by bells you mean a couple of nasty lifter ticks, that it.