502 "Canvas" - recommendations for reliable 550HP
 

19165956 Gen VI Merc EFI Long Blocks - low hours.
Removing stock EFI hardware and going Carb w Victor Jr intake
Closed cooling (own)
Gil exhausts (own)
Adding oversized oil coolers (own)

Heads look decent and very clean: Rev C 900-343944 stamped on them

So what would you do with them to get to 550-600 reliable?

CAM? Keep EFI CAMs or go 741?
If change CAMs - what springs and head work?
Carbs - which ones?
Bump compression or leave it? What head gasket?
Swap plug order?
What electrics?

Thanks

Swamp