Thats a great engine for the right guy.You would be lucky to find a good home for it.Like Tech always says,combination,combination...so I doubt you could tune it down enough to make you happy. I wouldnt sell it in pieces either.
You might try any local race car engine seller if you have any hard core sellers in the area.Or race track.It cost a lot to build an engine like yours and all the labour will be lost.
If it was me,I would run the engine until it was needing a freshen up or someone bought it after you scare the living poop out of them.Then build mamby pamby 450 HP 383. When the engine needs to be freshened,you can take it apart for potential buyers with no losses.
I know what you mean by the engine scaring you,,,,they are a handfull with that much power and a manual transmission