May be better off buying something that's capable of those figures "off the shelf" rather than pouring money into a model which would require a major investment in the hope of getting the same result.
The original Brera concept that housed the Maserati V8 was significantly longer than the mass production version. As others have said, it won't be as simple as dropping in the engine. Brakes, suspension, electrical issues -a slippery slope IMO.
I have the Autodelta re-map and while it's nowhere near as quick as the Maser, it's still fairly brisk.
Good luck with it all if that's the path you choose.
I've enjoyed way to many 'off the shelf' cars with the sort of poke I'm talking about, in the £50k to £300k bracket .. but I have a thing for Alfa's and really like the looks of the Brera but not the standard engine options !
I understand from various engineering summaries that the Brera Q4 seems to have been designed to cope with considerably more poke than its got with everything over engineered, which is one reason why its so porky.
I'm fairly keen on the idea of a taking a standard looking 2nd hand 2006/7 Brera Q4 bought for £10-£12k give or take, and then substantially modifying the engine/brakes/drivetrain etc. I believe I could end up with a stunning looking car with wolf-in-sheeps clothing performance when I want it, and for a hell of lot less outlay than the off the shelf options. I could go on at great length about how achieving the dream of owning various "supercars" is actually asking for epic financial losses, and a licence to be fleeced senseless by authorised dealers who are often not much better than brainless molluscs that work at kwik-fit. I've got 25 yrs of experience to back this up …
As for major projects in the past, the most drastic was when I took an old group B rally car, 4wd etc, weighted under 1000kg, and uprated it to 580bhp / 470lb ft. This began 15 yrs ago, and at the time it was capable of matching a Mcclaren F1 for its mid-range performance figures. I did actually use it for up to 3,000-4000 miles a year on the road as well as the track, and kept it running for 10 yrs before being offered an unexpectedly attractive offer to buy it when at a track day. The money from that went into another project which is a sort of track based missile, and one that I am currently trying to make road legal. However, its way way to compromised to be used as any sort of daily car, and will be incapable of lurking anonymously in a carpark. Its about as subtle as the 2005 Batmobile with pink spots !!
anyway ... I'm going way off topic as well ...