I'm with Martin. Hope you can handle another opinion.
1. Movie value to us and 99.99987% of the U.S population? zero
2. Movie paint job, real cheap, real cheap paint
3. What's to inspect? Look at it! There ain't much to inspect especially if it does not run and there is no battery. You can't "inspect" the trans, the clutch, the brakes, the gauges, the lights, the rear end or the motor except to see if it's frozen. You can't check for leaks (water, gas, oil, exhaust). So don't pay anybody.
You
can "inspect" for the presence of all components, you can see the body, the interior and the glass. You can articulate the suspension and steering. If the body is OK, that's 80% of the $$$$ risk done with. The rest is DIY and a little money. Plenty of parts. Inspections are irritating to sellers. Once inspected, what are you going to do anyway? Tell him it sucks here and there? tell him it's perfect? Change your mind?
4. Long beds less valuable than short.
5. Step side less valuable than Fleet.
6. First year for coil front, last year for wrap around windshield (expensive)
7. One year only grille
8. I like V8's but now it's a normal swap. Not original.
9. If title is OK?... good. No title with funky story...I would never buy.
10. Can't say money value without seeing it, and no one on earth can access the mystery movie value if you don't say what movie. Even then, it's still zero.
11. Forget Haggerty, please. You are CORRECT, your 62 IS your reference. Sans the frickin movie. Haggerty doesn't buy trucks, people do. It's all about regional influences, condition, U.S socio-economic conditions at the moment, sellers motivation, condition, originality, cool factor (OK, a movie) and condition.
I am sorry to be so blunt and I know that you are already going to buy it because you love the movie, not the truck. That's OK, the money means nothing and my comments mean nothing unless you ever want to resell and think you will get your money back.
Go for it and be happy. I have purchased a whole lot of trucks, sometimes I buy because I want it and ignore my common sense. Around here, that average, slightly rusted truck would probably be $3500-$5500. More rust, less parts present $1500-$3500. Ball park, as you said. In an Elvis Presley movie, driven by him, with his signature on the glove box door.....Boom! $5600.

You went looking for this truck, sellers knows that. Tried to buy for years, seller knows that. you want it because of the movie, sellers knows that... If you make him mad, you won't get it, you know that. Bottom line: You have no leverage on price. Fun stuff. Good luck, let us know.