You cannot compare the Canadian Dodge with the U.S. Dodge - they were in two completely different markets. The U.S. Dodge was Polara, Polara 500, Monaco and Monaco 500. The 500 models came in hardtop with the Polara 500 also having a convertible.
The U.S. Polara was priced to go against the U.S. Catalina while the U.S. Monaco went up against the Executive (Star Chief). In Canada the Dodge Polara went up against Plymouth Fury I, Chevrolet Biscayne, Ford Custom, Meteor Rideau and Pontiac Strato Chief.
For the Canadian 1966 Dodge -
PL - Fury I DL - Polara
PM - Fury II DM - Polara 440
PH - Fury III DH - Polara 880
PP - Sport Fury DP - Monaco
The two letters (DL, DM, DH, DP) are the first two letters on the VIN.
The three Polara series share the same taillights while the Monaco had unique taillights filling the chrome moulding on both sides of the trunk. Should also have Monaco in block letters in the section between the taillights and a small "Dodge" script on the left side of thr trunk lid above the taillight.
Your car has the Sport Fury interior, complete with the red, white and blue rectangles on the front door panels.
The three rectangles on the exterior are correct for a Canadian Monaco, but it is missing the "Monaco" nameplate on the rear quarter panels. It's also missing the moulding along the sill from the front wheel well to the rear wheel opening and the section to the rear bumper.
Should also point out that the 1966 Dodge built at Windsor, ON used the same body tag as used in the U.S. (for the first time) but no broadcast sheets. 1970 or 1971 was the first year for that at Windsor.
So, what are the first two letters of the VIN? It should be on the hinge post of the driver's door.