Okay, I'll bite:

16 heads, which I've bought 2 sets in the last year will run $350-$450.
Intake any where from $100-$150
Oil pan - got me, maybe $100?

So, $700 right there.

Carb and block are the only HO/WQ engine unique parts you've got. People are asking ridiculous money on eBay for blocks and carbs. They've also been listed there for years, meaning no sales.

So, optimistically, $2000 for both.

That get's me to $2,700. Maybe you can ask $3,000 if all the date codes make sense.

What you don't mention are correct original distributor which would have been shared with the regular 400 I think as well as correct original exhaust manifolds(long branch). Those two would get you to 4k in my mind mainly because of the long branch manifolds. If you can find someone looking for an HO engine. The difficulty in my mind with getting premium pricing is that the HOs don't command premium prices compared to regular 400s. Or at least I don't think they do. Maybe a 10-20% markup, I could be wrong as I don't recall seeing any 400 HOs sell in the last few years. It's nothing like a Ram Air car which would get 3-4 or more times the value of a similar condition 400 car.

If it were me and someone showed up with $2,500 in cash, I'd be loading them up as quick as possible.