I got exactly the same product (although round, not oval) for my Cobra because the 9" is just the right size to fit up into the hood scoop. I found that the factory K&N base, which is nicely radiused for increased flow, placed the top of the filter too high and there was no way the hood would close. Time to regroup.
I took an old "Mr. Gasket" 9" air cleaner assembly and used that base, as it was just a 1/4" flange that had no radius to the transition to the flat section on which the filter element sits. It worked, but I was not happy with the way the Mr. Gasket base interfaced with the flange gasket on the carb.
Eventually I decided to try to find a shorter filter, so I went to the K&N website and used their search function that allows you to input the dimensions you want. What I came up with was a 2" tall K&N filter element that was specified for a Toyota Corolla. I swapped that out for the factory 3" K&N element, put the K&N base on the carb, and viola...it fit under the hood and I can feel a definite improvement in the "seat of the pants" feeling.
I'm sure height is no problem under the back window of the GT40...but it sure was under the hood of my Cobra. There is no way to order the entire filter assembly with anything other than the factory 3" tall element...anyone want to buy a gently used K&N 9" diameter, 3" tall filter (LOL!!).
I really like the look of your oval filter element, though...wish they had been available when I bought my round one, but at the price (IIRC it was in excess of $150) I'm not going to swap for the oval one now.
Really, I like mine a lot...definite improvement in throttle response with that radiused base compared to the abrupt transition to the carb flange on the "Mr. Gasket" product!
Cheers!
Doug