For the stock supercharger, the most anyone has seen without nitrous is sub-300. A small shot will get you over that. The TVS guys regularly see over 300, easily, with some of the more 'built' motors seeing in upwards of 400. One guy has the record with the TVS at 421whp. Then he saw a lot of knock and blew a rod. He was on 10.5:1 pistons, all bolt-ons and a ported head, but only the exhaust side. He was the first on the TVS to reach that point, so I'm sure with many more people getting the TVS and trial/error, the secrets will be out on how to safely do it.
The turbo conversion guys... Well, one guy I know on the forums has a turbo swapped stock internal motor that made 440whp 385wtq. Stock motor! He has since torn it down to build it with pistons, hg, p&p head... etc. But again.. trial/error. I have a lot of respect for him and his car, but I just prefer to stay supercharged.