I'm doing an Alpha/Bravo conversion. As well as replacing the existing 454 with a more powerful 439. Can I run the Alpha triangle coupler or do I need to upgrade the the Bravo coupler?

You'll need the Bravo coupler. Depending on how powerful your 439 is, you may need the long snout 'HP' Bravo coupler. I'd use the HP if your 439 is built to rev like a bastard. I wouldn't trust the alpha coupler with a bravo drive and a HP motor though IMO.

Yes, its going to be reving somewhere between 6200-6500 rpms. So I'll start looking for an hp coupler. I figured that is what I would need but I wanted to make sure.

I would ask someone that knows better than I do but the guys I run with have 700-900HP Heats and I have heard them mention not to run a Bravo1 over 6K RPM's.

http://www.cpperformance.com/SearchR...CategoryID=439 try this or this one http://bpi.ebasicpower.com/c/MER6E/C...for+Mercruiser