You can certainly combine them into one tube. However, the oem system is acutally very efficient & capable of support well over 460 cid up to 400 hp- especially with a filter change.
If you do an online search for “air filter test” there is a lot of very good information. IMHO, the CAI units are NOT WORTH THE $$! Unless you are talking about a system that was specifically designed for a specific application there are very little hp/tq gains actually achieved in a street use vehicle and there are very few docs that these mfg’s can produce that actually show an increase in hp/tq in the power-band range of a relatively stock street vehicle.

I would avoid oil impregnated filters. While they have their purpose in off-road applications, Ford/GM/Dodge all have “watch-out” bulletins where the oil has contaminated intake sensors. - they even have a training video for the tech's on this (flatratetech.com) .

If you look at the flow data, WIX HP filters flow 98+% of K&N and have a much smoother flow post filter plus excellent filtering, for a fraction of the price!

You can use a WIX OEM HP replacement filter in the OEM plastic manifold box or build an true air ram type intake into intake.