I think i found a COPO engine Weird suffix

[964IMPALA]

Hi,I posted this in the Impala net and they tell me i possibly have a COPO motor any help would be appreciated.

Hi,all I purchased an engine recently 1968 cast# 3935440 It has a really weird suffix T0419I5 yea a 5 and the vin# 18D166508 I see broach marks in the picture on the deck pad so i believe it was a factory stamp.
I believe the D in the vin is Doraville GA internet says Impala was building cars there from 65-70
my info could be incorrect so any help would be appreciated..
Thanks 964IMPALA
One of the Replys i got from Impala.net forum
photo attached..

I was really stumped on this one and I toyed around with the idea that maybe the 5 meant an "S" (I also equals 1 sometimes for an example), but the IS was a '68 427. Your Casting Number also proved it to be 396. Anyway, I was just about to give up and I found this:

Drivetrain Decoding |

You very well may have a COPO Engine.

any help would be appreciated...thanks