Dunno where you are in this project, but given that you are doing the work because of low oil pressure, you should inspect or have inspected the cranshaft main and rod bearing journals. If they are withing tolerance, and not scored, get a set of STD sized(or if the crankshaft has been ground, the correct undersize. Old bearings would be marked, and a micrometer will tell you the diameter compared to stock grind.)
Get a good gasket set. If you want it to run reasonably well, don't bother with all the expensive parts. It will run well without them, and you are doing this for the first time. Messing up expensive parts on a first-time job is not encouraging. Do the job decently, but don't invest a lot in performance parts, until you are comfortable deciding what you want. No point in having an expensive set of pistons installed to putt around town.
My opinion.
Check the cylinders for damage & wear. Look at the cylinder walls for scoring, scratches, etc., along with checking for a ridge near the top. If you can still see the crosshatch machining marks and the ridge is minimal, measure for taper and out of round using a micrometer and a snap 'T' that you put in the bore, release, and then set. Remove and measure across. I do not have one, but you can pay a machine shop to do all that. Of course most will recommend boring, oversize pistons & rings, forged pistons, etc. You can get by with a standard set of most everything for a good while. No boring, no grinding, etc. But the journals and cylinder walls need to be in decent shape.
Remove the oil pump bottom plate and inspect the gear teeth. New pumps are not expensive, and if you find wear on the teeth, replace the pump. AND pickup tube/screen unless you can clean yours to bare metal, no gunk.(carb cleaner will do it, as will a 'hot tank', but new will work also. Get a good gasket set from a known maker.
I have done 'shade tree' work for a long time, and have had reasonable success without resorting to machine shop work in many cases. Most times, the cylinders are a little worn, and the rods/mains worn also. Just polishing the journals, and replacing the bearings got oil pressure back to normal. Cleaning the lands and grooves, giving the cylinders a light cleanup using a 'bottle brush', and replacing the rings, resulted in a 'freshened' engine that ran pretty well. Unless you plan on building a high performance engine, do a minimal job to see if you like the work and have an interest in dumping a lot of money into the engine. Anything you spend will NOT be returned if/when you decide to replace or sell. If I was told 'It has forged pistons, chrome rings, new full-floating wrist pins, Edelbonk bearings, Mullins oil pump, etc,', it means nothing. Who do you trust to actually put those things in properly? Who did the work? Are you sure they did not swap this block for that block? Performance parts are mostly hidden, and can be 'sold' even if they are not there, so the market for USED is very small. "was only driven short distances on Sundays by my aunt". 1320 feet distances? Who do you trust?
Sorry to disagree, but I'd limit by Buck$ invested in a first-time, and a 16 year old truck.
Do the job, using standard replacement parts, and see what happens. Sort of I don't care what the bores look like, replacing the rings, rods and mains should improve compression and oil pressure if nothing else, and that is the original problem.
I have no problem with your decision, either way. I just have had different situations where dollar$ were always short. I once did a re-ring of a Chevy overnight. Flipped the rod inserts as the uppers were more worn than the lowers, and replaced the rings after reaming the ridge. New head & pan gasket, and back together. Before it was 'fogging for mosquitoes' with blue smoke, after it didn't smoke at all. Back then, a set of rings was ~$12, gaskets ~$20, at 'Fleenors', a new "discount" parts store. Every other parts store sold at full retail. Anyway, it was a vast improvement, and it ran pretty well. Previously, oil was required at each fill of the gas tank. Cost was less than $50. My brother was really happy. No machine shop work was done, and we lapped the valves, as I remember, to get 'reasonable' sealing. We were not going to race a 235 Chevy stovebolt six with Powerglide. But I digress.
tom
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