76 chevy short step value

[82 Silverado 4X]

My neighbor has a 76 Chevy SWB Stepside that I'm looking at but he isn't sure of how much it's worth. He's owned the truck since 1979 and I've known him all my life so I know what he's put into it.
He did a frame off on it 10 years ago but never totally finished it. It's been stored inside since he stopped working on it. The frame and the entire suspension was stripped then painted Basecoat/clearcoat. All the body panels are NOS GM and mounted on a rust free cab. It has dark blue metalic laquer paint. The interior is stock and in excellent condition.
It has a 350 (.30 over) forged pistons, rods and crank. Aftermarkret cam and aluminum heads. Holley Pro-Jection Fuel injection. Performance built 400 Turbo Trans with a high stall convertor and a 12 bolt with 3.73 gears and limited slip. There is only 56,000 on the truck and 300-400 miles on the drivetrain since he put it together.
I would need to replace the hood because it was damaged in storage and it needs the wood in the bed replaced. No other damage or work needed.
He's only considering selling it because his collection has grown too big.
Any ideas what it's worth?