Yes there is an intersecting galley to feed the wrist pin from the oil scraper ring land, on on each side of the piston.
There is also one at the bottom of the wrist pin boss that is oiled from the squirters/splash oil.
You can try to dissolve, drill, dig out the gunk from the oil feed galley, but making the turn down to the wrist pin will be an issue.
Now the bad news is, trying to remove the pistons will not be simple.
In most cases the piston can and will deform in shape, crack or just shatter when pressed off the rod.
The wrist pin bore that is supported can end up "pinched" and not allow the wrist pin to move freely, it can be honed to fix this.
Some shops do have a special "piston press kit" that can minimize potential to the piston, but the risk is still there.
I am not saying that it can not be done, just the risk of failure is high.
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Personally, clean what you have the best you can, or just buy a new set of pistons and have them hung on the rods.
Odds are right now the used pistons you have are damaged in some way, shape or form, from scuffing on the skirt to be collapsed.
Have the pistons been mic'ed for size? Has the block been mic'ed for wear and taper?
With the cost of new NPR 63DT pistons and ring kits, and having the pistons hung and the block bored over size, would cost $200-$300 as a guess, based off prices in my area, I am sure they will vary in yours.
