Looking for more 408 pull at the big end?

I'd bet that the head is the cork, not the cam. A edelbrock head really isn't big enough for a stroked small block in a race configuration, IMHO, it's really a street replacement head for 340/360 combos

Even the Magnum version? Heck I picked that one myself. I WAS pretty proud of that!

Who made the convertor?

TCI Super Street Fighter 3500 stall converter