good point.....

If you want to make some serious power, ditch the stock intake and go with the large single plane and 2000 cfm throttle body. I know I wish I would have. I have had some serious work done to that intake and it is still holding me back. So, I get to do some more work on it this season and port the throttle body.

I think for what im looking for the 500efi intake will work great.....so......the big question is anyone out there have one for sale??? Please send me a PM if you do or know someone who does.

Which manifold?
 

I concur with Eddie Young and others here. I have done a lot of testing on 540 inchers and even some bigger cammed 502's with reworked heads and the like and even the stock EFI manifolds by Merc will top out just over 600HP with the best airflow you can squeeze from them with porting and the single mono blade throttle body.
Raylar has developed a whole new top plenum setup for the EFI manifold that we are using in our 675HP -525EFI upgrade engine exchange program and we get to 675 -700Hp depending on the cam we use.
For a simple MPI upgrade, buy the single 4 barrel throttle body EFI setup like Eddie has in his pictures and run that it will make all the power you will need with the minimum of investment and hassle. And no you don't need a 2000 cfm throttle body, a 1200 cfm will do just fine!
Ditch the MPI intakes, they won't get you there even close!

Best Regards,
Ray @ Raylar