Ready to replace my stock Gil exhaust manifolds on my 35 fountain's 500HP engines. Should I go with the conventional Gil replacements or Hardin Marine Cyclone "Shorty's"?

There is a $1,000.00 difference (Hardin is more) and I wanted to know if I will pick up any performance and if there is any down side to the Cyclones?
Thanks
Dan

Also look at Stainless Marine cast headers. They are dyno proven to be as good or better than CMI's.

i too am in the same boat...would love some input