If they are for a BBC...

The problem with Vee drive headers it the way the engine sits in the boat....A vee drive has the engine much lower in the front than a Jet, the Jet boat engine typically has the engine at a 3-5* up angle, the Vee 3-5* down making the headers point down as much as 10* too low in the rear, you definitely will have to check header to deck clearance...

I hope that answers your question.

GT