Hmm.
I reckon you could add at least another 100kg with the hypothetical LO engine (I say hypothetical because I doubt it'd physically fit!).
In reality I think a more sensible turbo conversion would be a cossie, or even a blown Zetec. Did once see a nice Hayabusa Turbo conversion. 8-)
I think the predictions for acceleration for the lighter cars are a bit optimistic. When the weather gets better I must take the Westie out with the AP22 data logger and see what it's actually achieving.
I think when power-to-weight ratio gets high the limiting factors are more down to gearing and traction. I'd be happy to get 0-60 under 5s without sacrificing grip in the wet and putting sticky tyres on it, splurging on a close ratio gearbox, etc. etc..
I reckon it got it about right for the Omega and LC, though.
The other issue is aerodynamic drag. Does it allow you to input that? Cd for an Omega is 0.31 IIRC. For a Westfield it's appalling. About 0.70. That will have more impact at higher speeds, so 1/4 mile time and terminal speed.
Kevin