[TimG]

There are Noverember, 11 390 horse Corvettes with ones and I's in the stamping. This stamp would be TIIIIIL for a November, 11 IL code motor. Even the I character is documented with different style I's. The car I saw had two different types of I's and a 1 used for this date code.
The key is other cars with engine stampings of the same date had the same features. These unusual cars will validate each other. A '68 L88 in Houston has a engine build stamp with a 1 in place of an I for the engine designation. This car was considered a fake or at least a questionable car until another '68 L88 that was the next car built turned up independently with the same feature.