Here is a quote from a corvette forum,
"68 and 69 l88's used a holey 4150 p/n R4054-A OR A 4296-A (ALSO USED ON THE ZL1) GM P/N 3925519 AND 3955205 respectively.
Here is the link---http://forums.corvetteforum.com/c3-tech-performance/684325-what-carb-did-the-real-68-69-l-88-have.html
Argue with them
I stand by my experiences, I am not an expert.
I am sure your customers liked the VS carb, I did too! But the MS suited my driving style better.
Good debate though.
Lou