I decided to add the car that member "slantzilla" mentioned initially in post #3083178 to my list (#55 "unknown29").
Reason is, he said it was a car with HP2-emblems on the fenders but with a 440 put in. As I assume nobody at that time would have retrofitted "HP2"-enblems to a car, that was not a real RL21H6.
Because at that time, you wanted prestige and everybody to see it. So if you retrofitted emblems to your car, my opinion is you would have used "HEMI"-emblems,.. as they tell the people prestige.
Instead "HP2"-emblems don`t tell "look, what I am".
Just my 2 cents.
@slantzilla: do you by chance remember any details to the car e.g. ext./int. colors, transmission. When and where did you see this car?