The numbers stamped on the RF deck are as follows:
The numbers on the LR ledge (behind the distributor and oil pressure port) are as follows:
You can check the casting numbers at
www.mortec.com which would reveal:
3970010....302.....69....4 Bolt...Z-28 Camaro
3970010....327.....69....2 Bolt...Trucks and industrial
3970010....350...69-80...2 or 4 Bolt
Basically, you have the generic 4" bore block used for about eleventy-jillion engines. At least it isn't a 305.
The design number will give you a little more information. You can decode some of that at:
http://www.nastyz28.com/sbchevy/sblock.html
If the engine is disassembled to any degree, you can usually find some hints in the timing chain area and at the flywheel end. If you find the numbers "010" and/or "020" cast into the block at those locations, that indicates the block is cast with an additional 1% tin and/or 2% nickel to aid durability, casting stability, and machinability. The tin also helps resolve inherent gray iron casting porosity. These blocks are generally considered better candidates for building to higher power levels, even if they are "only" two-bolt main caps. Actually, the two-bolt block are better, IMO, since they can be fit with aftermarket splayed 4-bolt caps which are stronger than factory 4-bolt (straight) caps.
