new member with some S3 questions

Hello to everyone,
this is my first time owning a landy a s3, 88 petrol, could anyone suggest what engine to convert to as the 2.25 petrol is very tired with a bent push rod. I would like to convert to a diesel if poss. any ideas welcomed as i am a novice.
thank you for any help given
Dirk

2.25 diesel, 2.5 diesel, 200tdi, nissan 6cyl diesel, mazda t/c (Perkins) 4cyl , lpg v8.
Got all of them in buggies. Best IMHO mazda diesel & hc V8 (petrol) - sh*t mpg but scared beemers at 120mph+. (90 front end and modded rad mountings)