I read a good deal about it before posting. I saw numbers from 250 to 350 at the wheel, 505 at the flywheel, and 435 from the factory on a stand. The upgraded engines of the L88 and L89s were underrated for insurance reasons. At least thats what several mechanics on the forums claim.
The only certainty I could derive from all this mess is that in 1968 L89 corvettes could dyno 500ish to the wheel when in the hands of expert mechanics. The 435hp number is from a stand when chevy detuned it to keep insurance companies quiet in order to sell a racing motor. This one was being transported from Mannheim/Hedrick automotive auction house to Barrett Jackson auction house in Scottsdale. Considering this one was owned by Hendrick automotive (I work at the Hendrick/Mannheim auction where Hendrick stores a lot of their collector cars) then was sent to Barrett Jackson for auction. I assume this one is mechanically near perfect because of the caliber of the sellers. therefore it likely is one of the 500ish hp L89 stingrays that mechanics swear is possible. Heres the sale information if you want to see nicer pictures than mine as well as the price:
moral of the story: thank god for ECUs