I agree with Lee on that one. Plugging the squirt hole is probably the cheapest and most effective way to make sure you have enough oil pressure at the front main bearing, and it won't hurt the engine. In all honesty, the only reason I went to a full flow oil system is that I was really frustrated with engine re-builds. I had to re-grind the crank 3 times in the first 1000 miles on that engine because of junk in the galleys. First time it was a rear main seal that destructed after 5 minutes of run time, the second was some kind of locktite that hardened in the block and went through the galley and tore out the mains...Now me working for a engine filter company, well I just could not take that kind of abuse, so I got kind of twitchy and had the full flow system put in.
If you are not concerned about junk in the galley, I would really consider just removing the oil filter system completely, plugging the squirt hole, and running like that. The oil pressure will be great, plenty of flow to the bearings, and the oils in production today will easily withstand the heat from these old engines. And honestly I don't think any of us drive these trucks enough in a season to wear out the oil.
Back at ya Lee, we need a ride.