If anyone can help me answer my question I would greatly appreciate it. I have what a guy sold me as a 5.3, but I am wanting to make double sure it is. (I bought it for dirt cheap) If anyone has some info on how to identify this motor I would appreciate it.

 

Whats the block #? Should be on the front.

Whats the 3 digit # that is stamped on the head on the top corner as well?

 

If the pistons are flat tops usually that indicates that it's a 4.8

 

the pistons are not flat tops. the head casting on the corner are 862 I believe. I would have to go back to the shop to make sure.

 

862s came on both the 4.8 and 5.3. If they are dished then it is definitely a 5.3

 

It sounds like you have the heads off if so stick a tape measure down the hole and if the piston is 3.66 inches down then you have a 5.3 if it only is 3.27 in the hole its a 4.8.

 

Easiest for sure method is to pull the pan and check the crank casting numbers

Block and heads are shared between 4.8/5.3