wacw, I'd go with the Holley 390. You've got the 4BBL intake, why put a 2BBL carb on it??
I've recently upgraded from a 350 Holley on a 2BBL intake to a 390 on 4BBL. As long as I'm just cruising around the 390 gets better fuel economy, but of coarse that all goes south when all 4 barrels are opened up
Even with the secondarys "locked" shut with the heavy black spring and using it as a 2BBL carb while tuning the primarys, the responsiveness of the 390 is a lot better than the 350.
I know my engine is a different build to yours, I just thought I'd share my experiences of these 2 carbs. Don't get me wrong, I still think the 350 Holley is a great carb for a Slant 6 (my old Val ran mid 15sec 1/4 miles with the 350) I just think the 390 works better for my setup.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

Hmmm...no one's even mentioned the Dominator...

No comment

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Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

Not when you can buy 800 and 850cfm Thermoquads at swap meets for $10 and drop a kit in them!

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Or save your money and just throw them away.

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Official Cookie and Mater Tormentor.