That's a big project. I never like to see "found" vehicles with systems "open". Things like oil fill cap off, carb uncovered or missing, cooling system open are invitations to rodents. I picked up a Ford flathead V8 years ago that looked really good sitting on an engine stand. When I got it home and began tearing it down to inspect I discovered that rodents had been in the water jackets. It took a looooong time with furnace brushes, long tipped air blower tips and compressed air to clean and blow out all the debris. Thankfully, there was no debris in the lifter valley or in the oil pan and the debris in the water jackets was minimal but it still took a long time. That engine is currently in my Model A Hot Rod and still running great.
You're going to have to inspect that engine in the truck very well. I recommend pulling the rocker cover, oil pan and water pump to check for rodent debris. The oil pan is going to be the biggest PIA if you are going to leave the engine in the truck, but that also gives you the advantage of checking the oil pickup screen for gunk. Do all that before trying to start the engine. You can check to see if the engine rotates by hand before doing all that. A cheap boroscope to look in the spark plug holes at the cylinder walls would be a good idea. If the engine is "free", you're half way there. If not free, a 50/50 mix of auto trans fluid and acetone in the cylinders to soak (be careful, acetone is HIGHLY flammable). That may take weeks to work and get the engine unstuck but you can cross that bridge if you come to it. Luckily, the carb was covered so hopefully no water in the cylinders. The oil in that canister filter is blacker than sin. Not a good sign, but not a deal breaker. If the engine is free and there is no rodent debris in all those places you can attempt to start with fresh oil in the engine. Liberally pour some oil over the rocker shaft, get some Marvel Mystery Oil into the cylinders, check and adjust/replace the points/plugs, etc. Crank engine over without power to the points to get the new oil through the system and to get the cylinders lubed up a bit with the Mystery Oil you put in them. Then attempt to fire it up. You can do that with the water pump off and the rocker cover off. If it runs, only run it BRIEFLY (you don't want to overheat an engine with no coolant in it) so you can quickly check to see if oil is coming out the rockers (you want to see that they are getting oil). Make sure you have oil pressure with a good gauge hooked up. The carb may be in need of a rebuild so you may only get it running and keep it running with gasoline in a squirt bottle down the carb throat (the fuel pump is likely no good as well). Do not try to use the existing fuel delivery system as it probably needs a good going through to clean it all out. The fuel lines and tank are likely gunked up, etc. A friend to stand by and help is always a good idea when doing an initial startup on an old engine. Fire suppression equipment close at hand is always a good idea. Big rags to cover the carb if flames appear is also a good idea to snuff out the flames but be careful the rag doesn't ignite.
Good luck and let us know the progress.
Andy
