Truck has been in a garage for over 15 years

[A-Rod]

I recently bought an 87 v10 silverado and the truck has not been started for over 15 years. The gas tanks are a mes the fuel pumps are rusted and the radiator is leaking. I need help or advice on what to do before trying to start it. I was told to take the spark plugs out and spray wd40 on the pistons but not sure. I did turn the engine with a wrench so i know is not locked up. Any feed back will help thanks

[Captain Swampy]

Pull the plugs out and disconnect the distributor so you can spin the engine without compression to get oil to the cam and valvetrain. You probably need to rebuild the TBI unit. It's easier than rebuilding a carb. Yes spray something in the cylinders, maybe 2 stroke oil or engine oil. Stock fuel pump is AC delco EP 386 but I think the EP 381 works and has better flow.

[gunrac]

Drop the tanks! I'd even replace all fuel line. between tanks  and engine. Filter is a given.

White vinegar an hot water work as good as anything you can buy. 2-3 bucks a gal. Mix vin. to water 60/40, "more is not better". Then add about a 1/3 or so Gal. of nuts and bolts. Seal outlets. Shake occasionally. Rest tank on all side an ends. Try to keep tank wet. It will take some time, but works. Get ya a telescopic mirror and flashlight to check progress. It will eventually shine. Rinse w/water accordingly, after your satisfied. Stuff a hair dryer in it, dry to where you don't see or hear water. Finish out w/Acetone. It will dry out what moister is left. Seams and or pin holes. Also, you want to consider a quality sealer, inside and out.     

[hatzie]

Pull the distributor and pre-oil it with a drill and oil pump priming tool just as if you just finished assembly on a stand.  You can use a pressure pot attached to the oil sender connection to blow oil through just as you would on an LSx engine...  Do this first before you do anything else.  It'd be a bummer to spin the dry crank bearings when it could've been avoided by a quick prime.

I use ATF or Marvel Mystery Oil through the spark plug holes on an engine that's sat for a long time.  Once it's primed...  crank it over by hand with a wrench till it spins free.

Just replace the fuel tanks, fuel pumps, senders, and fuel lines.  They're cheap enough and they won't be full of pinholes.

The brake lines are probably pretty crunchy too. 

Check that the water pump isn't seized up before you spin her over.