oil pressure drop

Cam bearings could be the problem. Was the oil pan full of oil goo? Are your oil ports in your heads clear so the oil gets back down to oil pan and pump. Most of the high mileage motors can get gumed up even if you changed the oil regularly. If a cam bearing spun just a hair it could cause oil pressure problem.I wouldn't invest to much trying to fix that tired motor. I would guess by the SB on your post that your dakota has a 318 cubic inch motor in it. The 318 is one of dodges most reliable motors and has been used 40+ yrs. It might be more cost effective to replace motor with a lower mileage 318 with a warranty. You should be able to get one anywhere from $600-$1200. All depends the mileage and condition. Btw if it did spin a cam bearing you are probably going to need a motor.

the heads were clean,just flushed the strainer never dropped the pan.It's a 4.7

The oil pump and strainer/oil pick up tube are in the oil pan. Who or where replaced oil pump & strainer? If you don't mind me asking. I love a challenge.

when he was changing the pump he drained the pan then poured gas through the top no backup then blew air through to make sure it was clear.

how do you blow gas thought that I have not done that before.