Simon Philips from Vic has Datto 1200 Coupe turbo for U2L, it uses highly modified A Series engine, Jordan drove it at the 2018 Tailem Bend Nationals. It's power to weight is pretty effective being a light chassis but the rpm limit of the pushrod valve train is a bit limiting. When it was N/A he dabbled with a Honda CB 1000/1100/1300 cylinder head, which would fix the valve train issues and let it rev to what it could do. It's big advantage over the N/A U2L is of course torque, at 21 psi it would have ~50% more torque than the best N/A engine.
A couple of guys have had a go at turbo Mk1 Suzuki Swifts (they are pre 1986), just destroke them to 1200. But getting a transaxle in them to handle the torque is not easy. Plus cooling system, driveshafts, uprights, etc makes it an expensive exercise, with pretty much everything being bespoke. Compared to the off shelf gear for Hondas, Nissans, Toyotas etc. Someone with the time and budget will do it eventually, but it will require patience and lots of engineering effort.
Cheers
Gary