Yep, peak power on the 318is is usually around 6k rpm.
The M42 is fantastic engine and there are plenty of ways of getting more power out of them. Got a couple of mates with 1.9 conversions pushing out 160-170bhp which didn't cost them much. It's also a popular engine for bolting a supercharger on or going for a 2.1 conversion. Loads of people are doing lots of fun things to them!