>>53781097>100 or 114 special>104 speedThose are pretty good stats for gen 1.
If it gets to keep moves that don't exist in Gen 1 then Delphox is probably an OU allstar. It has guaranteed special drops with mystical fire, huge damage off fireblast, thunderpunch to beat waters, and is the only pokemon with a good fighting move in focus blast. Although that uses it's much lower 69 atk stat so you're probably better off with just psychic. Also with modern calcs Delphox using psyshock hits Chansey about as hard as Tauros using body slam does for a 3HKO unboosted.
Should nasty plot work like amnesia in gen 1 it might even get kicked to ubers for being diet mewtwo.
If we limit this to only gen 1 things though I could still see it being played in OU even if it isn't tiered there. Psychic typing is superb and having 104 speed hypnosis plus firespin cheese as a backup would go a long way. I think it would be the best firetype at the very least.