Here at my shop I do LS swaps all the time. Turbo, nitrous, blower, been there done that. I love the LS engine as I think it is a powerful compact, plentiful engine that can go good for cheap.
But I wouldn't put one in my T type for one reason. Turbo Buicks earned their rep BECAUSE of the LC2. The ENGINE is what made them a legend. If I put an LS1 in it I now have lost the essence of what makes the car....the car. The whole point of buying one in the first place for me was to own and drive a legendary, rare different and valued member of our automotive history. It's the same reason my 70 Stage1 GS got detuned and is getting a restore to stock(although it's always had a BBB in it.)
If I want to go faster than an LC2 will reliably take me I will buy a regular Regal and proceed to let the welders fly. Any sane individual wanting to go single digits in a car is gonna need cage, fuel system, rear end, suspension and brake mods anyway. At that point there will be so little left of a stock GN what's the point of cutting it up when it's worth more sold as a stocker to get revenue to buy a cheap N/A V6 car to build. Never understand cutting up true collector cars into hot rods when you can usually buy a lesser version, badge it and build it for less....yet it looks the same in the end.
That being said it is his car, he can do with it whatever he wants. However, just like a buddy of mine when he found out his new tube chassis race car(bought already done)was originally a 1970 Stage1 GS, he may be crying in his Cheerios if the value of these cars goes through the roof. I personally take a different view. One less left with the original setup means my car gets more desirable and valuable if a family crisis ever arose and I needed to sell it to make money.