Don't spray the 'nitro' with the platinum plugs. For a 75hp shot, I'd go one step colder copper plug (personally I like the autolite coppers) and close the gap of the plug to .040-.045. However, NOS reecommends a gap of .035
www.sparkplugs.com should help you in cross referencing plug brands.
And yes, the 2.5L can handle a 75hp shot. The rule of thumb, is that an engine can 'safely' handle 50% of its stock rated hp via the nitro. i.e. 2.5L = 200, so it should be able to safely handle a 100hp shot.
