Vortec 5.3 vs 4.8 identification

[kihm]

Is there any way to ID the engine size from outside, there is a Gen III engine at the junkyard that is really cheap, $300 with no accesories but the guy form the junkyard doesn´t know what engine size is, I already have the casting number 12577396, but it is the same number for both block sizes.
It also has a sticker on the outside that says FJB in big bold letters.
I know that you can tell by opening the oil pan and look for the casting numbers on the crank, is there any other way? thanks in advance.

[WhatsStuckK5]

Not too many other ways. the only way i knew mine was a 5.3 is the fact that it has the flex fuel injectors, which are were only on 5.3s in 02. the pistions and crank are seriously the only things that are typically different. sometimes the small stuff, like i said injectors, may be different, but unless its flex fuel, theres not much other way to tell...

[88smurfj]

The blocks are interchangable The only differences are internal. For $300, it is a good deal eather way.

[1969x11]

you might try to shine a light in the spark plug hole to see if the pistons are dished or flattops. dished-5.3, flats-4.8.

[kihm]

Thanks, I'll try that...