Well fast forward a week and a half, got a friend with a rollback to haul the truck a few miles down the road to the my house, unloaded it and drug it around to the back of the shed to clean out the cab and start tinkering on it! I removed the spark plugs, seized carb, and valve cover to get a better look, other than some acorns and stuff, the rockers were really clean! Shot some PB Blaster down the cylinders and was able to rotate the crank with a strap wrench! I think we got us a possible runner If the engine is in good running order, it may just find its way into my '58 3800!
Though there is one thing I noticed on this 261 engine, it has been rebuild. The head is from '55 (date code B-11-5) but the block is from '59 (D-29-9). Block casting # is 3759365, the prefix is difficult to make out but I can see an "L" on the end (6000 series truck engine). And also see a tag (most likely from the rebuilder) thats been riveted into the front of the block, but its halfway covered by the water pump.
As for the truck itself, I originally bought it just to save it from getting scraped and would use it as a parts truck. But after thinking about it, the truck might end up becoming another project. Repair the fixable rust, different engine, swap axles/wheels, and building a flatbed might be in store for the ol 6500!
Oh and here's a shameless plug to my YT vid of this truck