The 164 is a fantastic car, but its not as good as an Uno for some things!
Parking, chuckability(3 or 2 wheel cornering!), simplicity, cheapness of parts, lightness, economy, the van like boot when you fold the seats down etc. These are the things I LOVE about my Uno!
Also the insurance for a 164 is alot higher than the Uno here.
I`d like a Fiat Coupe, its reliable, got rear seats for my kids & looks lovely, BUT I couldnt carry as much in it as I do in the Uno (my mountain bike for example). That goes for the 164 too.
The Alfa GTV is also gorgeous, I`d love one of them too, but it has the same downsides as the coupe.
To me, if you want to stick a turbo twin cam in a small, spacious, simple Fiat, it makes infinately more sence to do it to a Tipo, its virtually a straight swap!
In fact if I didnt have the Uno, I`d have a 1.4 Tipo instead (I`m kinda keeping my eye out for one anyway).
The Bravo is a very attractive small-medium hatchback, but lacks the boot & interior room of the Tipo & is alot more complex electronically (& slightly less reliable as a result). In theory the turbo twin cam (or even the 5 cylinder turbo) would fit that...
So, if you wanna stick a turbo twincam in anything, get a Tipo, if you feel like going really mad, fit the 4wd system in too (from what I can work out its a fairly simple swap).
But, if you want to upgrade the Uno, stick a 1.6 engine in with the turbo & gearbox (& loom & mountings) in from a UT.
Its logical to me anyway!
I ought to write a FAQ on this, as I give the same cynical answer every time
Have a look at
https://www.fiatforum.com/uno/171352-2-0-16v-turbo-into-uno.html - I think that's the most useful thread - not only do you have the doomsayers Chas and myself, you also have a couple of people who have actually DONE the conversion
This time though we have a new angle on it - price - I think if you have to ask the price, it's probably not economic to do the swap.

I'm fairly certain that it will be more cost-effective just to buy a FIAT Coupe.
Have you already exhausted all the tuning possibilities for the Uno Turbo 1.4 engine? You have a hybrid turbo and front-mount intercooler? Considered larger injectors and 1.6L bottom end? All of that will be cheaper than a Coupe engine + conversion + certification + insurance. Plus I reckon the finished hi-boost turbo car would be faster, lighter, and more fun to drive.
I'm biased but I reckon the best answer for cheap power is to buy an Alfa Romeo 164 - 200bhp for less than £200 complete car and I reckon better to drive than a Coupe - I don't think any engine swap into an Uno Turbo can match that value for money, but I would like to be proved wrong!
-Alex