Ported Slant 6 head

I'm just curious, and I used to want to hotrod my slant 6 real bad...

Why don't the EFI conversions just use motorcycle throttle bodies and a side-draft manifold, instead of the carburetor-style manifold and carb-style downdraft throttle body?

It seems it would be pretty easy to make an intake for side-drafts...

there are a couple side draft intakes... there is one cast by lynx and clifford that uses 3 SU carbs and another to use webers...

i like the SU carbs and know how to tune them so i would have no issue in doing so... its just kinda pain to switch over to them