Well the L&B is a 3 series based kit, with a single donor you'd end up with a 2.5 litre straight six
, however the single donor concept is no doubt the future.
The guys at Factoryfive sell more kit cars then most. Check out their approach at factoryfive.com. All you need is their kit and a single donor car then you have everything to complete your build! Pity them Mustangs aren't that common over here and then of course the taxes importing from non EU countries, say no more...