Outer Limits 4x4 Board

G'day everyone, was just wondering what lbf/in pressure cap should be used on a 1985 Rangie with a heavy duty radiator. ie the cap on the expansion tank. mine is currently a 15 pound job, but my expansion tank has recently cracked along a seem, mostly due to age but got me to think that the pressure might be to great. The radiator bloke, thought they should around 7-10. My workshop manual also mentions 15 pound maximum capacity for the cooling system. Any idea's as what is best to run?

Cheers

I thought it was 13 lb.