3 blade, 4 blade, 5 blade.. Aluminium or stainless steel? What are you trying to achieve (Speed, towing, smoothness)? And what is currently on the boat and what RPM are you getting at Wide Open Throttle?
That engine have a 2 bbl carb or a 4bbl, or MPI? And does it have vortec heads or not? (What would be the most helpful, and you should include it in every thread you start, engine year, and full description, like 4.3LX, and a serial number).
And :welcome: to iboats.
Chris.......