Fun video. I once owned (bought new) a 1970 Road Runner that was the same color as that GTX. It was a base 383-4 making 330hp. The GTX time slip of 13.91 @ 99.44 tells me it's factory stock. However, the Challenger 440-6 time slip of 12.24 @ 115.66 tells me it is not factory stock. Factory stock times for a 440-6 Challenger/Cuda were in the 13.6 @ 104.4 range. That said, that was a fun race to watch. I wish it was a 1970 Challenger 440-6 vs. a 1969 Road Runner 440-6 (both factory stock).
I went twice, years ago w a friend to attempt to buy a 69/70ish GTX 440 6 pk 4 spd car. Had the cool vacuum hood scoop...my friend had $100 bills stacked up and fellow wouldn't talk of selling. Car was getting kinda rough but was all there, factory correct & ran. Story was the man's son bought it used when he come home from Vietnam. Was killed in another vehicle wreck riding w his friend. Dad would mow the back yard, move car to other side of the yard to finish mowing. Never left the back yard. Never found out whatever happened to it.