I have a 1995 f150 4x4 with a 5.0 302. It also has a manual transmission. The truck has no power shifting through gears. I can barely get it over 40 mph.

timing chain may be off a little, chevk coil for spark loss

Double-roller timing chains either work or they don't. I suspect that you may have a plugged catalytic converter. You can connect a vacuum gauge to verify that or many muffler shops are willing to do a flow test for next to nothing. You can also try the "Shade Tree" method of dropping the exhaust at the Exhaust manifold (loud, I know) and see how it runs for a short time. The oil pressure concern is generally the Oil Pressure Sender - they've never been very good - screw a new one in before getting too concerned about it. They're cheap.