I feel your pain. I've been there.
Each build I do, I do more of it myself and I think that's the key to success. When you do it yourself, you are careful and take everything into account and there is no risk of the apprentice working on it at a workshop or someone forgetting to tighten a bolt.
Good luck with the new engine.
FYI my last race car was a 2L RS2000 Escort and it had Motec throttle bodies on it. I put it all together myself and power did improve over the Sierra single throttle body plenum manifold I had on it previously. I lost mid-range torque though. You really need to rev the tits off an engine with throttle bodies to get the full benefit. Make sure you change the cams when you do the build.
BTW you can get throttle bodies that don't have butterflies - when they open, it is a big hole - nothing in the middle. I can't remember who makes them though.

Barrel valves and flat slides. 
 
Those are like having a turbo engine with constant issues to have running well 24/7. They have downsides also (jamming and part throttle openings etc)
 
 

also guillotine throttles take up a lot more space, and barrel valves are super expensive. Heres a quick summary from jenvey:

http://www.jenvey.co.uk/j...els-or-slide-throttles

The Donut King car (Exige V6 Cup) that Neil/SSC prepped won by reliability in the end, it was not without its stoppages though, it had two lengthy stoppages, one for a SC belt, other I cant remember.  The Ginetta was beating it in pace and reliability up until it failed to finish.  The Exige V6 was the only car to finish in its class, but a win is a win and thats endurance racing.
 
I cant see a 1320 ever doing 680hp, I have one on my car, I think at 420hp they would be getting reasonably close to maxing it out.  But I could be wrong.

Neil only gave me the hp number and nothing else. also do not know the exact spec on the sc so its all guess work.
As for the itb's, its not top of the list. There is still the idea of running the stock lower intake with a larger plenum and a large single throttle body. The larger plenum would have velocity stacks going straight up instead of to one side for clearances.
The priority is having the engine reconditioned/built with some portwork then get it installed and running. Right now, its still sitting in the workshop waiting for the 3SGTE to be sorted before starting on the 2GR.

Would itb's with a plenum around them perform much better than an intake manifold with velocity stacks and just one big throttle body?

Yes
 
 
 
 
 
 
 
If designed correctly

kameleon
Yes
 
 
 
 
 
 
 
If designed correctly

Any info on who can design it correctly?

The plenum chamber or the throttles? Ideally you would have a selection of ram tubes that you could change on the dyno as i doubt there is any info out there as to what is "the best"
 
Plenum around throttles is easier to get right.

Hey Steve maybe you should build one of these engines instead. Insane!