Glad you primed it before starting. Its most likely the oil pump. The older 6.5 pumps did not have the volume needed to supply the extra needs of the oil squirter blocks. Doubt you did any harm to the engine running it with low pressure. IIRC 10 psi is the low spec at idle. As long as it did not drop to 0. You should be ok.
The beauty of the Second Amendment is that it will not be needed until they try to take it
If Americans ever allow banks to control their currency. First by deflation then inflation. The banks will deprive the people of all property. Until their children wake up homeless.
1998 GMC K1500 WT, 6.5 TD. 80,000 miles. Auto, 3.73 gears. Remote PMD mounted on the radiator support. KOJO tune WOW! Carter HD lift pump. Feed the beast, GM8 turbo with Hurricane impeller. K&N filter. Ported, gasket matched upper intake. Leroy's braded stainless steel oil lines.
New Bosch injectors. Flow matched 2200 lbs pop
3 1/2" custom Aero turbine exhaust. Nutered Cat
2" Lift RS5000 Shocks. 285 X 17 Bridgestone AT summer tires. 12.50 x 33 x 15 Procomp MTs winter. Powertrax No slip locker in rear.