1970 LS6 Engine,CE, Original carb and distributor, air cleaner opinions

[1969camarors427]

I am looking at a LS6 engine that was a warranty exchange engine in 1972, It had the short block and heads both changed at the time of the warranty repair.
The engine was removed from the car in 1974 and the owner has had this engine as he owned the car it came from since 1972.
He was the partsman in the 70`s at a GM dealer that has sold many Hi performance cars including a 1969 Copo Camaro that I owned back in 2000.
It has been in his garage since 1974. In about 1986 the motor was taken apart and new rings and bearings were installed to freshen it up to put in another car.
The car was driven approx. 200 miles and then the body had some repair and the paint stripped off. Since then it has not moved. He would start it up from time to time then he would just turn it over by hand.
We have been dealing on this for about 4 months. He wanted to do some research on pricing before deciding if he sell it or keep it.
I have a LS6 Chevelle and thought it would be a good spare as it is complete engine less the original exhaust manifolds, alternator and starter.
It comes with the original Cowl induction air cleaner, original Carb and original distributor and all the deep groove pulleys.
I am trying to make a deal on the engine. It is not a over the counter engine. Here are some of the part numbers.

BLOCK
3963512
H18 70
CE155xxx

HOLLEY CARB
3967477-GG
LIST 4557
013

INTAKE MANIFOLD
3963569

DISTRIBUTOR
1111437
9M 10


First what would you value the engine, less bolt on parts, air cleaner, Distributor, Carb and pulleys.

And what is a fair price to sell the carb and distributor as I already have them if the deal happens. Looking for a fair price to both buyer and seller.

I just want to pay a fair price for the engine, he wants quite a bit for it ($11,000) as he said it is most likely worth more to him than anyone else as he has had it since 1972.

The 70 LS6 car was sold in 1974 when he removed the engine and eventually totalled.

Any help/ opinions would be appreciated. Thanks.