cig20

iTrader: (1)

does this number mean any thing was stamped on block above timing chain cover
107025 xk

MILD THUNDER

iTrader: (3)

I think on some blocks that was like a manufacture date/plant type of code. I could be wrong

The casting number that is more important is on the rear of block, just above the bellhousing flange. Certain castings were better than others

FIXX

iTrader: (2)

back in the day,thats how gm use to code their engines,,454 ls 5,6,7..a letter for the hp rating..

cig20

iTrader: (1)

fix
any idea what this would be

FIXX

iTrader: (2)

ok ,,when you hear the term number's matching when buying a numbers matching car thease are the numbers you need to look at..those numbers and letters tall you where the engine was casted,what date and type of vehicle it belongs in..their called suffix engine codes..you can try google.. try chevy 454 engine suffix codes..

lakematdude

5=GM s model year. In this case it could be 1995 1985 or 1975.

GM Engine Codes
The model of MerCruiser engine can be determined by looking at the last letters of the engine code
that is stamped into all complete long blocks. This engine code is stamped into the long block by
GM at the time of assembly.
If the engine serial number, and/or model decals are missing, the engine code will help to determine
the engine model. Refer to drawings for engine code location.
Information you need from the engine code, example V01115MD.
5=GM s model year. In this case 1995, could also be 1985 or 1975.
MD=type of engine. A 350 cid V8, MerCruiser models 5.7L Bravo, 350 Mag, 350 Mag Tournament
Ski.

Unfortunately, you're xk did not make the mercruiser list. Like fixx mentioned, Maybe googling GM's Engine Code Identification will help.

http://www.marinemechanic.com/merc/d...blockcodes.PDF
http://www.boatfix.com/merc/Bullet/95/95_05.pdf