stock oil pump for hp use

66Dartman has asked a question here which has me wondering also!

At what point in a build should I decide to fit a hp spring into a stock oil pump? or is it better to buy a high pressure oil pump?

Is there an accepted rpm, or bearing clearances that make it necessary to build in more oil pressure?

Sorry 66Dartman I don't mean to hi-jack your thread but this has rung my bell and I need to know!

Regards,
Steve