There is a way to insure that the cylinders are in good shape without running the engine. Its called a cylinder leak down test. It requires a leak down tester. As for bearings there is no way to tell without hearing the engine run but usually low mileage engines do not have this problem. Its always a crap shoot when you buy a junkyard engine so if you buy, just buy at a good price.
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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "