Mopar R1 block

I had a friend with a 71 challenger RT convertible 446 pack car. The car that they weren’t supposed to be built. But sure enough it had the right Vin and fender tag
Kind of my dream car. I’d probably give my left nut for one.
My 1st grade teacher took me to the Chicago auto show in 1970
When I left with her from school, to spend the night at her fiancés glass tower apartment downtown, it was in her 70 Challenger convertible B5 blue, and blue interior white top. It was new.
I’ve always had an attraction to a Challenger, and prefer the look of the 71 better.