[Marv D]

Rick have you checked the gauge and verified it really IS low oil pressure. My 94 dash gauges are 'old and tired' (like me) but are CRAZY inaccurate. Temp shows ~150 at 180, Oil PSI shows 75 when at 55psi, and volts,, ... well ya just never know, anywhere in the sweep from 8-15 is ' normal'. I added a set of pillar gauges with a trio of Autometer gauges and they are not 'perfect' but at least consistant. The stepper motors in the stock dash get horribly 'crazy' when they are old and tired. (again probably more like me than I care to admit)

ONE thing to keep in mind here,,, 5-30 oil is a 5wt oil, with polimers that tend to 'string together' and make the oil act like a 30wt oil at 'normal' engine temps (200-240°) The idea is to have the grat flow capabilities of a 5wt oil when cold,, and 30wt when hot. That said,, the additive package that is supposed to make that happen is SUPER high-tech stuff added to a 5wt oil. The better the quality of the aditive package the better this 'morph to 30wt happens. I'm still not convinced it really does 'change' to 30W I mean I look at it this way. IF it did exactly what the 'theory' says it is supposed to do, it would have the same oil PSI cold as it does HOT.
When internal components overheat due to lack of lubrication, the expand, you get metal transfer and cold welding till things simply seize. My thought is components are all expanding and oil clearances do grow, without a doubt bu tthe oil PSI drop (cold to hot) is JUST AS MUCH the oil's fault as it is loose components. Loose oil clearances allow the THIN oil to escape more easily.

That said,, IF your gauge is verified and right.... try a 40wt diesel oil and see what happens. All of the discount houses have a 'house' brand, as does Dello and Rotella are offered in straight 40wt

As far as changes to the motor,, If you keep the TBI your going to have a PIG unless you have a new prom burned for the OBDI ECM And TRUST ME on this,, finding someone that knows what the heck they are doing and can get you a GOOD tune is hard (if not IMPOSSIBLE) to find these days. Even the chips to burn are getting difficult to find a source from what I hear. I did to my 94 4x4 what your considering and believe me,, if I had it to do again,, NO WAY, I'd toss the TBI and ECM driven distributor and put a stinking CARB on it. WAY cheaper and WAY easier to change the tune.

For my 94 I used a later 1piece rear seal block so I could move to a hudraulic ROLLER (I refuse to build a flat tappet ANYTHING any more) , did a 3.75" stroke (383), Coated Mahle forged pistons, Scatt I-beam rods ,bought a set of RHS Iron vortec heads, Had a GMPP Vortec / TBI intake bored to accept a 670CFM Holley throttle body, (at the time that was the ONLY Vortec TBI intake available, but now I believe there is a knock-off available for WAY less than the $400 the GMPP were then)
All in all I think I spent right at $5500 building a BAD Dawg 4x4 Vortec stroker TOWING motor. THEN came 4 different chips trying to get the stupid thing to run right.

ALL that considered,,, Throw a long block at it with a fresh TBI and enjoy the simplicity of what you have. OR if your exempt from emmissions and inspections, throw a carburated 383 at it with a MILD cam if you really want to make enough torque to shred the 25year old trans and differential.