Isn't it about 5 grand for either of those, so hardly cheap? I also considered the supercharger route despite the cost, but rumours of single figure mpg put me offthere is a Supercharger upgrade to the V6 and also there is a 3.8 conversion that Autolusso do
thats more likely to be easier cheaper
If you only have a Twinspark GTV to start with, (a nice one, say £1500's worth), then the cost of a 20VT transplant if you can do the work yourself is basically the cost of buying the donor car, I've seen rough but running Coupes fetching little over a grand lately. Obviously you'll belt it & clutch it etc while its all out and no doubt change lots of other parts too, but you'll pay the same just buying a V6 in reasonable order. Fiat Coupe is at 260hp with a simple chip upgrade and making 320hp is do-able for under a grand.Surely it's got to be cheaper and easier to go down the route of super charging the Busso engine such as the Autodelta kit.
Probably more powerful and you get to keep the gorgeous Busso sound too