"Murica" lives in this thread
I'm pretty sure not only do CAFE standards come into play here but the fact that the Euro market gets the turbo model only factors in....
Then there's insurance, ...
You do know there's 400-500 hp 2.3L Ecoboosted Stangs around already, right....
...hmm, kinda funny how my 406 s/b powered 78' Caprice would beat BB's all the time,...
...when I had my 87' GN too and here's what I'd say....
... the GT-R, 3.8L
Well aware of the "Global Marketplace" that we all live in these days. I know that surely comes into play, especially as the engine "platforms" are much more of a 'global' thing
these days than they EVER used to be.
Insurance isn't necessarily less for a turbo 4 than a V6. Back when Mazda started offering turbos on the RX-7 (
around 1990) we almost bought one. The operative word being "almost".

That was when I owned my towing business, and ran across one that was an undamaged recovered theft vehicle. The car was flawless, leather, heavily option loaded. So I called my insurance agent to get a quote, (
we had a brand new 4Dr Accord LX at the time) and was told that their "rates" stopped at $2600 a year and didn't go high enough yet to cover the "turbo", and that it would be considerably higher. OMG was it higher! Quote came in at over $3200 more than three times what we were paying. We didn't end up buying the car for just that reason. (
And we didn't have any tickets, owned our home, were married for over 13 years, and had a 2 year old.)
Fast forward; Today a vehicle offering a 275HP 2.2L turbo or a 272HP 3.7L V6 and the V6 will be cheaper. Now if it's a 1.5L "T" and they are puffing it just to get it moving and it STILL can't keep up with a V6 (
if that model even offers a V6) that's a different situation all together. :xyxthumbs:
Oh yes, I know all to well that guys/and girls for that matter will 'tweak' their 2.3L to get the absolute maximum out of it. That goes EXACTLY to the point I was making however, in that
that engine has the durability of snow cones on pavement.

Were I wanting to have a reliable monster torque/horsepower beast I'd look into the Ford V8 "scorpion" powerstroke upside down diesel engine or the GM 4.5L Duramax that Ford pulled the design cues from. :dblthumb2:
(Although GM scrapped the plans to produce the power plant AFTER Ford copied it.)
Note that the exhaust is where the intake ports should be! Then the intake is pulled through the valve covers to the BOTTOMS of the heads. That with 4 valves per cylinder and a TON of horsepower for a 6.7L. It really is a beautiful design!:dblthumb2:
First Look: Ford's new 6.7 Powerstroke
But for that 406, that's still cubic inches. Same thing with a 427, that's still a small block.

I'd rather have the small block all things being equal.
Now that Buick GNX was, (and still is) something very special for it's time. Turned into quite the collector vehicle too!

rops: Even then though that was only 245HP from those 462 Cubic Inches, (276HP from the
very limited GNX). That's twice what the 'non' turbo did though. Neither was exactly earth moving. Buuuuuutttt.... that was the mid-80's and NOTHING was earth moving, which is what made the 276HP GNX such a special power plant.
Annnnndddd that brings us to the 'modern era' of high revving, high performance V6's of today. As you said, "the GTR".
I have one of those VQ engines and they are schweettttt, to say the least. Putting twin 'screws' on one and you can have rock solid 550HP (at the wheels) all day long. Yet even that package will pale in comparison to a 5.7L small block putting out a normally aspirated 550HP. :hotrod2: