PM Chris155 on here, he lives in the North West, somewhere near Chester I think.. There's not much he doesn't know about V6s and I reckon he's done more engine swaps on his driveway than most main dealers!
SteveAlfa has been in touch with me but as I have 2 projects on the go at the moment, I don't have the time or the space for 2 additional cars. I don't think replaceing the engine is necessarily the best or the most cost effective option either. Its sounds as thought the water pump has failed causing the engine to overheat and warp the heads.
At this point I would be inclined to take the heads off and see how bad the damage is. It may just be a case of getting them skimmed and bunging them back on again. The problem with this is, out of the 2 v6's that i've looked at that had overheated, 1 of them had run a couple of big end bearings as a result. I suppose it would depend on for how long it was run after the head gaskets failed.
Realistically it would perhaps be better to take the engine out to repair it as Removing the sump on a v6 isn't as straightforward as it is on a t/spark. Which kind of brings me back to the idea of swapping the engines.....
Engine Swap estimated costs:
Donor car: 3-400
Cam kit & Water pump: ~250
Clutch kit (stupid not too really): 150
Oil, filter, coolant, gearbox oil: 50
Plus labour for:
Remove engine out of donor car
Remove engine out of to be saved
Remove box, replace clutch
That's probably 45 - 55 hours work for me as a minimum.
I'd then be left with a broken 2.5 engine and a car with no engine in it....
Where as, on the basis there's no bottom end damage:
Cam kit & Water Pump: ~250
Head skims: ~100
And around 20 hours labour.
Regardless of this my best advice is still to take it to Just Alfa Spares in Aintree, they'll be able to mitigate parts costs, they've got the space to do either option or even supply and fit a new engine, they'll also be quicker than me and in all likelyhood, cheaper.