Help ID'ing this LS
 

New to the Forum. Please cut me some slack on this total newbie question, but I've been all over the net trying to decipher exactly what I've got. This engine belonged to a friend who passed on and I have no documentation other than the casting. I think it is a Gen IV, but that's about all I've been able to come up with. Also, there is another casting stamp indicating the engine is a 4.8/5.7. I don't understand how it could be both. Any info based on these numbers gratefully appreciated. Semper Fi to any Marines out there.

12598301
10 179 07
10
The number 07 in a Circle (Mfg date?)

https://cimg8.ibsrv.net/gimg/ls1tech...490d2394d6.jpg

You're looking at casting numbers for the rear cover. You need to be looking for the numbers that are actually on the block. Theres one that is just below the deck surface that will tell you what it is.

4.8/5.3 (NOT 5.7) is a block used for both the engines indicated, the only difference being the stroke is shorter for the 4.8.

And a longer set of rods in the 4.8

Good catch! Forgot to mention it. Main point for OP was using same block for both. Thanks!

Thanks for info, guys!
 

I'll get some numbers off the block as suggested. Appreciate all the help!

Those blocks can be safely bored to 5.7 for what it's worth then all the LS1 one stuff will fit..

The only downsides is you have to drill/tap one hole in the block for the accessory bracket, and you will have an engine about 100# heavier than an aluminum block version.