Trying to figure out which iron 5.3 i own evidently its not as easy to figure out as i had thought. Been talking to a sleeve manufactorer and they want to know which 5.3 i have. Engine code is 12551358 than follows GMSM00. Heads are 862's also have 1005r9363865. Lets see if you guys can help

 

U tryin to figure out if its a lm7 or lm4? Or if its a 4.8 or the 5.3?

 

If its a lm7 or not. Has the proper 5.3 dish pistons or lack there of dish is more like it

 

If it's got factory flat-tops then it's a 4.8L , or if it's an aluminum block it could be an HO 5.3L

 

so since this is iron block aluminum head its either lm7 or l59, anyway to tell them apart? is there any REAL differences??

 

Also i bought this on craigslist a while ago out of a "tahoe" no VIN or anything good to reference too.