You bring back memories; As you know, no diesel can accelerate as fast as a gas engine but if I still had my 1.8L VW engine, I would give it to you to drop into any VW of your choice. With 11:1 pistons, oversizes stainless valves and a hot cam, the only thing that prevented that engine from exceeding 7500rpm, was the point ignition! If you do want to rebuild a foreign engine with high performance parts they are available. However, I spent over $3k on parts and machining on my little VW engine!
I did have a friend who bought a used
Saab, albeit, a 900 turbo, and he put two new transmissions inside of 6 months and a few months later he blew the turbo. Having the car for less than a year cost him more than $5k and he bought it for $1500. Needless to say he was a real hotrodder.