3.0l twin turbo, depending on turbo choice and strength of the engines internals can get you to the the moon, no doubt about that eh zender?, i run a modified 300zx twin tub myself,
but lets not get carried away, as far as i know the desired build plan did not include a switch to rear or all wheel drive, but retain the 145 original layout of front wheel drive only,
so that alone will limit the extent of the tuning allowed by the 145,
that, and budget i should think?
power is nothing without control, as pirelli once said, and a 500hp 145 will either tear the gearbox in half if the clutch ever held it, or put you into the first ditch under uncontrollable torque steer
fun whilst it lasted though, ha ha!!!
i'd seriously love to see a V6 145, 2.5/3.0, 12 or 24 valve, they'd all be good in my opinion, some more powerful than others, some easier to fit than others, and some cheaper to tune than others, but no two ways about it, the fiat 20v turbo route is easily the most cost effective route to a driveable, useable, diy do-able, 300bhp targettable rip snorting 145!
a good donor car will set you back about a grand give or take a ton or two, then allow for a few custom extra's such as a decent fmic, some pipework and wiring changes, and you'd probably want to do a decent service ion the donor motor whilst its out too, cos its tight once its in!
a budget of £1000 to £1500 should see it done to a respectable spec i reckon, and leave you with plenty of donor car and 145 spares left to fleabay on to get some cash back, or put it towards a nice big Garret and Map for some more pony!
thats what i'd do, love to do with my 155, only once i'm bored with the V6 thats in it though,
and thats not yet, long live the Busso!