The actual runner length also includes the length inside the intake ports, so you are likely to not have the entire length as an external dimension. But for tight engine compartments, automakers like Ford and others sometimes have a 2 pc. intake with the plenum being removable and often the runners come outward from the head by a certain amount and bend back over the engine in a U shape. You still can get the desired runner length in a tighter more compact space. Engines that rev much higher and need a higher RPM peak manifold need a much shorter runner, so they usually don't have clearance issues under the hood. I have one Slant 6 race EFI intake i've made have adjustable Ram Tubes so it can be fine tuned a little more precisely. Look for a Ford 300 EFI upper intake on ebay and you can size your plenum around that as a baseline, since they are close to the same cubes as the 292.
