Solved - NEH 2369: 1974 Cadillac de Ville with 21-foot GRP body

[Carnut]

Describe what this thing is accurately and you will be awarded 1 point:

ANYONE FOUND GIVING ANSWERS GLEANED BY USING GOOGLE SEARCH BY IMAGE MAY BE BANNED FOR AN INDETERMINATE PERIOD!

[Carnut]

Experts?

[kwgibbs]

Any connection with Spohn?

[Zerk]

Base car 1984 Oldsmobile Toronado?

[bubenator]

I see DeVille bits.  Rear skirts and lower fenders look to be pre-downsize DeVille.  Front bumper looks like the 1973-1976 style.

[Zerk]

Wondering if all the molded-in parts are done neatly or just bondoed. Overall I'd guess the look he was going for was '50s-'60s GM showcar.

[bubenator]

This lovely creation showed up on ebay a while ago.
Rumors abound that this creation was concocted in the vicinity of George Barris. Whether he actually built the car for the former aerospace engineer or whether the engineer-turned-builder was an associate of Barris isn't very clear, but someone spent a lot of time on the ...ahem... creation.
It started life as a 1974 Coupe DeVille.

[Carnut]

Any connection with Spohn?

None, except maybe the inspiration..

Base car 1984 Oldsmobile Toronado?

Wondering if all the molded-in parts are done neatly or just bondoed. Overall I'd guess the look he was going for was '50s-'60s GM showcar.

Not Oldsmobile, no.  I can't imagine what he was thinking; this car is over 21 feet long!

This lovely creation showed up on ebay a while ago.
Rumors abound that this creation was concocted in the vicinity of George Barris. Whether he actually built the car for the former aerospace engineer or whether the engineer-turned-builder was an associate of Barris isn't very clear, but someone spent a lot of time on the ...ahem... creation.
It started life as a 1974 Coupe DeVille.

And this is indeed the right answer.  I don't know who made it, but it doesn't look Barris standard to me at all..
Well done.