1) In my experience, silvertop housings are far more resilient than blacktop ones to the temperatures of turbo engines. They also have M12 tappings for Ford or aftermarket CWT and a spare one at 1/8" NPT (can be increased to M12). They do sometimes weep around tapping insert but that is easily fixed.
2) If your feeling loaded, someone in USA does a 'billet' housing in a nice anodised finish for around £200.
The problem, I feel, is not restriction of a fully open thermostat, but the marginal amount of cooling from what is, after all, a standard 2.0l radiator. You don't even have the slight respite of an air/oil cooler as it has a water/oil cooler as standard. So first thing to explore to address the root cause of the issue is a better radiator IMHO.
Martin