There were two other Dick Harrell cars on Bill Allens lot the day I bought my 69 Chevelle - one was a Camaro for sure but I don't recall if the other was a Chevelle or Camaro. Don't know of any other DHPC cars and have never come across a single one out in the real world. . .
A friend loaned me a "Chevrolet by the numbers" book this evening - I noticed the following in section #2, 1969 Engine Code Identification:
MODEL . . . ENGINE . . HP . . TRANS . . . . . . . . . . . . . . . . . . . .SUFFIX
Chevelle . . 427 . . . . 425 . . COPO 9562 4 SP. . . . . . . . . . . . . MP
Chevelle . . 427 . . . . 425 . . COPO 9562 TURBOHYDRAMATIC. . . MQ
The Bill Allen Customer Invoice specifies Motor number "TO409 MP"
I suspect a typo somewhere . . .