"there software" is the 8th vin digit, that is all there is too it, that's what they useIf you're buying a used engine from a wrecker their software will tell them what engines are compatible to yours. You'd have to trust them on mileage and condition but to a point you can verify some of that before installing, like how clean it is under the valve covers, use a camera to check the cylinders etc.
any online seller will list the vin digit with there motor offered any worth there salt anyway
for instance vin c, vin z, vin t, vin f, etc
for instance here is 2,300 VIN C (L83) motors listed they can go in a pickup or a suv doesn't matter as long as the vin digit matches
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