Originally Posted by hammertime
There really isnt a horsepower level that you "must" have one. They are a great idea no matter and with the issues your having, its a even better investment.
Moroso 3 vane is the ticket IMO
Its also worth a few more HP. I have seen as much as 25hp on 565 on the dyno. I run moroso 4 vane with line on the back of the block, pulling from under the intake.
Good luck
Nice car BTW