It ain't stuck. I'm bettin your money on it. Soak it, search on frozen/locked motor advice. Rock the truck in 4th with 5 guys after spark plugs removed and pistons soaked. (center distributor plug removed).Look into plug holes as best you can with a good light to see rust or? No water in oil, no oil in water, probably OK. You DO need the history of the "lock up". If you already drained oil, was is dark or brown/tan? Just dropping the pan and looking at deposits in pan and looking at crank shaft/rods/bores, etc can be a good idea for confidence. You can also take off valve covers and see that nothing is "tangled" or broken. I see your profile says" restore old Chevy trucks for fun. So am I telling you things you already know? Do you do your own work, other than rebuild?
