I haven't found too many normal maintenance parts hard to get so far. Granted I don't look for those in the junkyard and rarely shop at the local chain stores, but when I do go to a chain store they can usually have what I need the next day.
Why give button pusher AutoZone the money, when I can get the exact same part from RockAuto for half the price. Might take a few extra days to get, but that isn't a problem. If the button pusher was value added sure, but I've only found that once. She was very much value added and I was buying all of my parts in store for the duration of the engine swap and rebuild into my Ranger. I was in O'Reilly at least once a week from January to July. I made sure to buy a few things at a time and spread it out for a reason to stop in. Of course I couldn't admit my real reason and the excuse given was spreading out the expense. She got a better job about the time I finished up getting it running and I've hardly been there since. I know where she works now, I need to stop making excuses not to and go visit.
Sorry, I was rambling there and I already do that enough without getting off subject. So, back to the topic at hand.
There are a lot more self service and salvage yards out there than that company, and there are a whole lot of parts sitting in them. I'm not going to limit my searching to a single year and drivetrain. Many parts are direct swap between the years, and many of those that aren't can still be used with a little effort. I do understand that there are som items that are a bit more specialized like the intake tube I was looking for last week. Move away from things directly conected to the engine and transmission most parts are interchangable regardless of if it is a V6 or V8 (or I4 for the Ranger owners).
I just took a gander at Car-Part.com for reference I searched for a 5.0L 2wd rear driveshaft for and Explorer. Seven pages of results at 50 hits per page. Changed to AWD rear driveshaft and it gave another 19 pages. That's over 1000 hits for potential donors from yards that choose to list on there, there are many that don't and no self service yards are on there.
I had to get creative trying to replace the stupid crook shaped molded vacuum hose under the intake manifold plenum, and ended up routing bulk hose
Yup, I'm coming down off of ignition and vacuum leak issues.
I'm dealing with that on my Ranger V8 swap now. I retained the Explorer heater pipes, but if the molded hoses ever become completely obsolete, I'll remove the pipes and run straight hoses like the V6s did. Atleast the ones in the 4.0L OHV Rangers went straight from the intake and waterpump to the firewall with a valve in the middle, no hard pipe.
I seem to have a leak in that vacuum manifold too. Mine is on the nipple for the back line. Don;t know if it's leaking under vacuum, but it was under the pressure from my smoke machine. I don't think the line is bad I think that it might be routed wrong around the fuel hardline, and holding the hose at an odd angle. When I have the intake back off to replace the injectors I'm going to reroute the hose and probably add a spring clamp on the end.
Thought for replacement on that PCV hose manifold just occoured to me after reading your post. When/if I have to replace those vacuum hoses, I don't really want to run bulk out around the plenum, and that bend is probably tight enough to kink/collapse the hose under the intake. What about making a hard "crook shaped" line? Take a piece of tube in the right size, bend to shape, then use short pieces of vacuum hose to connect at the ends. Throw some black paint on it and it'll hide under the intake like a normal vacuum line. Piece of copper tube would be easy to bend and likely last for ever under there. Throw a slight flare on the ends to help with hose retention, though it probably wouldn't be an issue under vacuum.
