[Veep]

Jenvy throttle bodies come with DCOE bolt spacing. They'll bolt right up to Weber manifolds.

https://store.jenvey.co.uk/throttle-bodies-and-components/throttle-bodies

But how does this answer TS, who is asking about turbo system?

 

[Veep]

Building a Twin Spark - naturally aspirated. Nothing too fancy -- good cams, aftermarket rods and pistons, ported head, etc.

sensible decision. I never seen the use of turbo in 105 chassis (yes I know the GTA SA....). Besides that you need the very long gearing of f.e. the berlina automatic (easy to find....)...
Seen a few going sideways (to far...)
Friend of mine did build one long ago (before the www existed...) sold it off, not very noce to drive. Other one was totalled , going straight on a wet motorway... (still not cleared why as far as I know...but probably due to tarmac imperfections..).
nice torque of TS will make a nice driver (which still does well in modern traffic)