I'm only interested in being helpful to you, don't want to sound like a Beavis...
All those rusty spots are much larger on the opposite of the sheet metal. They would need to be cleaned up and painted on both sides of the sheet metal ASAP to help prevent those areas from rusting any more.
I'm pretty conservative with $$$ $5500.00 does not buy much these days, so even in it's condition that we've all seen from your pic's I thinks its a fair deal.
Being a big block makes it better to me, not that many made. A board member here argued that point here....
I'd get it all cleaned up, that tired paint looks good enough to take a buff job and look nice (or nice enough).
Definitely trailer it, BUT you really need to be there to inspect it first hand.
I see it's got a Holley spread bore carb on it. I wonder if it's a 650 or 800 cfm?