I never realized they ran the vin format the same that early ...I always assumed it started in 67 (well I have never had a car before 67)
but a "P" second digit should mean GT, L is for the dart line.
not sure about D (must be an early A thing)
They used that through 68 anyway. My books don't go any farther than that.
L-Dodge Dart
P-Premium (GT)
23-2 door hardtop
D-273
6-1966
2-Hamtramck
Last 6 numbers-sequence number
My 68 is LH23B8B LOL and the B-body is RS23U0E which is the same format as his early dart. that's cool