Making sure this is alright due to using parts from a 71 and a 72. I have a E36 intake manifold (believe this was from a 71), no water jacket going to carb.

Then I have the 72 insulators with the water jackets.

Going into the 72 SUs with water jackets.

Ok, now for the air box side of the SU's, I have the 2 air ports at the top which I believe feed the damper.

But my air box only has the one opening for the air port.

Does this all seem compatible? I am currently not running the water line thru the intake, so I do not suppose there is an issue with the insulator but wondering if I should be using the earlier insulator with no holes. And for the air box only having one air port opening whereas I am just blocking off one of the air feed holes to the SU, not sure whats up with that and if I should drill that hole out or not.

On a side note if I need to change the air box (gaskets not that great of shape), thinking of just changing over to the K&N filter such as listed here: http://www.ebay.com/itm/K-N-Custom-reusable-cleanable-Air-Filter-element-56-9096-/350523313506?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3A240Z&vxp=mtr&hash=item519cd14d62, not sure of how to run the float bowl breathers or the flow guide breather. Seen a couple posts asking about this as well but didnt find any info on what people ended up doing.

Does the backing plate only have one hole in it like the gasket?

I'd stay with the stock aircleaner. Able to pull cooler air in from upfront, has good stacks built it, and feeds both carbs from a common air source. The individual air cleaners supply each carb from a different source (potential unbalance siuation) and pulls hot air right off the exhaust manifold. Also you have to make provisions for float bowl venting and come up with seperate air horns.

The backing plate has 1 hole, the gasket has 2. Here is a little bit better picture from the other side.

Not really sure what year backing plate this came from and if I should have the 2 holes that feed thru to the carb dome.

You learn something every day..... or should. Just asked Steve the owner of Zed Therapy about the hole thing and he pawed through his pile and said almost all his backing plate have ONE hole, Every so often he'll see one with two but the second hole has been drilled. Roadsters and SSS setups all have both holes in the backing plates. I pride myself on having very limited knowledge on this subject because for several years getting us out of the aircleaner business was a primary goal of mine.

Hmm, wonder whats up with that. If I understand it correctly those holes feed the dome area air, the housing is notched out for both sides to feed it air, wonder if this is just one of them universal type things where it was manufactured for multiple purposes.

Does anyone have any input as far as the air box only having the one breather hole going to the dome. As Bruce mentioned, some people drill out that second hole, curious if there is any benefit or harm associated with drilling out that second hole.

It will only matter if the hole is sized to control the rate of air flow. This seems unlikely since the purpose would be to control the movement of the suction piston and the motion is controlled by the oil damper.

I cut the stacks out of my stock aircleaner and match cut them to carbs. looks good. just have to get seperate cleaners.