A slant was in a 69 charger and they was going to ripe it apart here in northeast Arkansas just north of me 15 years ago and it was snagged up by a buyer from a Memphis TN. A collector or a spotter at George ray's drag strip ask about the motor and it was in there shop, Dark green outside and inside paint, roomer was it is in Big daddies stable of cars.
I would think it would be best to leave it as a / and have one of very few made, auto a/c charger and the int was ripped up bad.
Challenger may be a different story, But I can't remember seeing a slant in one in my life time so it has got to be worth more and show better as a / Challenger
my pennies worth