Hi new to the site and have a question regarding Air Cleaner set up..... I picked up a functional hood for my '72 Formula 400 and would like to order the Ram Air cleaner with the dual connecting boots however, in the Q-jets place is a mechanical secondary 700cfm Holley Double Pumper. Will the cleaner work with holley carbs and still mae to the hood correctly?  Also what is the best Rear Main to install, the one piece rope seal or is there a two piece seal that works even better?  
Thanks  

Hey welcome aboard!
I can't say for sure if the ram air cleaner will fit the Holley, but my experience is that most Q-jet air cleaners don't fit on most Holleys. Maybe someone else can fill you in on that one.
There are two styles of rear main seal available for your 400, the original rope seal and the BOP Engineering 2pc neoprene seal which is available thru their website. Though I have the rope seal in my Formula, I suspect the neoprene seal is easier to install than the rope seal and by it's nature is likely more forgiving (harder to screw up).  

I make a Ram Air Cleaner housing that fits both Holley and Q jet carbs. It is made in the USA, very high quality part but different than OEM style Air Cleaners.

You can see it at:

http://www.schmidtmotorworks.com  

It will be less painful to pound out an aftermarket Ram Air Cleaner to fit over your holley double pumper. That's what I'm doing, found an aftermarket base for $125 new. Saving my original as is with the the Quadrabog...

Someone on ebay is selling a two piece seal for the pontiac check them out.. Rope seals are difficult to install to not leak but it has been done....  

The machinist that did my 400 had both. He said since the Pontiac isn't made like a Chevy with machining on the crank surface where the seal rides to direct oil away from the seal he didn't care for the new design. He had one and said he would install either one for me. He also said that he had contacted the people that make them. When he questioned them about the differences in the crank surface he was told that nothing is perfect and all of them will leak. The second point is the new rope material is now a fiberglass type of product not the original asbestos type. He installed the current type of rope on mine and has not leaked on yet. But is not an easy task to install one properly for the non-pro like myself.