How many classic car insurance for a V8 Chevy Silverado 1985 would be 350?

A 1985 Chevy Silverado would not be a Classic Car. It wouldn’t be a “Classic” anything until it reaches at least 30 yrs old. It’s doubtful that the truck would ever be considered a “Classic” anyway. There’s nothing special about the truck. Hundreds of thousands were built and are still on the road now.
You can ask an insurance agent about that kind of insurance, but you’d be throwing your money out the door. Having several “Collectible” Classic Cars, the insurance isn’t cheap. Plus if you plan on driving it on the street, the cost goes way up! You’re better off just getting liability insurance and just drive it.