Did the 502 ever come stock in any vehicle?

Nope. Factory produced anyway.

A boat is a vehicle, and 502's were stock in many (such as the 1996 Scarab 26 I own).

I do not believe so. Muscle cars from the 60's and 70's had 454's as the biggest and the newer 8.1/496's were in trucks for a while.

Years ago I saw a 197? cadillac with 8.2 Liter on the front quarter panel. Not sure it was factory though.

My friend in high school had a cadillac, back in 1984. I don't know what yr the car was, he got it from his aunt. It had a 502and was front wheel drive.

The Caddy motors were 500" not 502". Think architecture similar to the Olds/Buick 455 vs. the Chevrolet 454.

You are correct. Caddy was a 500 not a 502. TURD's for motors. Not sure how they came up with the 500

you mean other than the trucks? I know they came in the 2500 pickups.

You are wrong. They were never installed from the factory in any on road vehicle.