[Chris L]

Thanks David, so I can assume a 2" thick filter sitting on your carby would extend to the front of the bonnet lip if it were 12" (300mm) long only just, assuming the mount flange is dead centre of the air cleaner, allowing for 150mm forward/150mm rear.
If that's correct then a 15" filter would extend approx. 40mm or 1.5" under the bonnet lip without fowling the height (80mm clearance/ filter height = 50mm). I'm assuming my new manifold and throttle body combined height is similar to your manifold/carby combo.
Maybe I better stick with the 12" version and give myself a chance , being a little to cute will bite me on the ass, particularly when I cant do the measurements on my own car !!
Appreciate your time
Cheers
Chris