This might be what the dealer was talking about. Here is some 1970 Model Year Info. It does mention the 1969 Camaro 396 as it relates to the 402 introduced in 1970. See page 7.
1970 New Model Summary
And information on the 402 Mark IV Block
400 Cu. In. Engine Released
However would not apply to an earlier 1969. That would have probably be a green block issue.
Greg