offy 4 barrel with Dutra Duals question?

I assume you are using the modified factory rear 3 banks dutra with the Dutra casting front 3 banks. If you do not plan on driving in the colder months in TN, use the block off. If you plan on driving all year long I recommend not installing to help warm uip the engine for better drivability. I just picked up an Offy 4 barrel intake with a holley 390 myself. I haven't put it on yet because after all the research it isn't going to do a whole lot with out a port and polish job on my head. I have decided to leave the twin one barrel intake on until I can get a new head and get the work done. Sounds like your on the right track with better exhaust, I haven't got mine yet. Good luck with your build.