The original poster signed UK below his name, so I would think that his
questions pertain to the European model. If I remember correctly, the
single-row timing chain in the 1981-1983 models is a US version problem only.
Also, the US model is indeed underpowered at 155 hp SAE net, but the European
model is much better. It had either 218 PS DIN (215 hp SAE net) in the early
version or 204 PS DIN (201 hp SAE net) in the later version. I would think that
this extra power over the US version 380 SL and lighter weight (no 5-mph
bumpers, etc.) makes it a better performer. In addition, the 380 SL had a
4-speed auto which would probably make it a better performer than even the US
450 SL. Also, the less powerful of the two Euro 380 SL versions (201 hp SAE
net) was still more powerful than any of the US 450 SL models.