An easy and fairly painless method of checking the stroke ia as follows.....pull out one of the spark plugs. Then turn over the engine till you reach TDC. Then stick a pencil or lenght of round wood dowel or someting similar and turn over (by hand) the engine till the piston is at the lowest point of stroke. Then note the length and measure. 3.5 for the 360 3.8 390 4.0 for the 428 etc... this will give you a fairly accurate reading of the stroke of the engine for you to determine what it is. Sure it's possible it's been a rebuilt 360 with a 390 crank but if the guy does not want you to remove the head to determine the bore this might help you. As others mentioned it could host any array of parts or be stock so be sure what your looking at and use the info Viking posted to help. It's easy once you know what to look for and where. The casting numbers tell all...............G.