No reason it can't be done.
The choice of the throttle body size would make or break it for how well it drives at low throttle openings.
A large throttle body with large chokes will be fun at high revs but useless at low revs.
My thoughts would be a 40mm throttle plate with 32mm-34mm chokes but a professional tuner would be able to give better advice than me.
Weber throttle bodies are easy to find in a range of throttle and choke sizes.
Design your manifold around the Weber bolt pattern and you will be able to tap into this large range of parts.
But don't do what that Ebay auction did.
He joined the shafts end to end.
The end throttle will not move quite as far as the middle throttles and gives trouble at small throttle openings.
Have the accelerator drive a single shaft, that shaft then has individual rods attached to each throttle body.
That way all the throttle plates will open at the same time and will have exactly the same opening (critical for fast response at low revs).
With care, you could choose to keep the Toyota ECU and injectors or choose to go aftermarket ECU.
And Weber throttle bodies have the choice of using open trumpets or a pair of rectangular filter pods.
Measure first to make sure you have room to put the filters on.
You might have to use a downdraft or angled configuration instead of sidedraft.
Of course, $$$ may be the final arbitrator.
6 ITB's cost a lot.