This isn't the block number right? Cause the owner says this is a 350/350 which would be 3932388?
Lots of numbers to discuss when dealing with Corvettes!
The number that you referenced, 3932388, is the casting number for the block. This number is located at the back of the block, left (driver) side on the flange that mounts the bellhousing. Actually three (there is a fourth unverified) distinct castings were used as the basis for ZQ-3 (350/300) and L-46 (350/350) engines in 1969. 3932388 is the early casting that was used... Followed by 3956618... And finally 3970010. The car in question was built in late February 1969 and is a bit early to have used the 3970010 casting, but I could see either of the other two being used.
For your 1969 L-46 application, a casting date, when the block was actually created at the foundry, is located on the right (passenger) side of the bellhousing mounting flange.
The deck surface at the front of the block on the right side extends past the cylinder head aproximately ¾" and is often called the "stamp pad" although it is really nothing more than an exposed portion of the block deck. On 1969 Corvettes there are two numbers stamped into the surface. The first is the assembly date/broadcast code which identifies the assembly plant, assembly date, and engine application and was stamped at the engine assembly plant. The second is the serial number derivative. This is stamped at the vehicle assembly plant and ties the engine (and other parts as mentioned) to a particular vehicle/serial number.
There are also addition foundry numbers and codes which are cast into the block, some known while others remain a mystery. Typically these numbers aren't relevant to many people and don't play a part in identifying an engine.