Stock Z Comparison (76 to 78 style is missing It looks like 75 but with more pollution fittings)
Bob Sharp Racing Intake, note the symmetrical entry of pressurized air between runners 3 & 4
12 Injectors/ 2 Fuel Rails (most people just use larger flow injectors)
LD-28 Diesel Intake
These 4 pics show a simple structure. It looks like bell mouths and tapered runners could help improve things.
One neat tip from the above is that a stock manifold can be chopped and a new set of runners and exhaust formed. The stock manifold's connecting flange can be recycled to save considerable machining.
RB-25/26 shaped manifold adapted to an L28e
RB-26 manifold for comparison. Note the bell like runner entries
TVM Intake variations
Cannon Intake Runners
From excellent turbo boost Maximum Boost by Corky Bell (buy it!)
Weird and wonderful ideas
Here is a concept for an easy way to improve air flow in a normally aspirated 6 using stock throttle bodies and some fabrication.
Two 55mm throttle bodies each feeding only three runners.
The inputs can be Y'd to a single input and then fed from a larger AFM or ideally, run from a non AFM/MAF reliant EFI system