... The climb rate I see on Wiki is ludicrous and is the climb rate at what might be cruise power. Nothing with a weight to power ratio of 5.0 lbs per HP climbs at only 2,500 fpm. At WER it was well above 4,500 fpm according to pilots who flew it. At military it was well above 3,500 fpm...l.
Yes, according to Dean's AHT P-63 was the best climbing late war USAAF fighter.
There is info on P-63 testing on Mike's and Neil's site P-63 Performance Tests