I've just come across a cam in a GM performance parts case.Written on the case in pen is MERC 465-500HP.On the cam end is stamped CRANE H-240 329-2-10.Below this is 13-9-89 which i guess is a date.I've looked everywhere for this number with no luck.Any help greatly appreciated.

RMBUILDER will help you out. I'm sure he will reply to this.

That cam is Merc Part# 485-816709 (Crane H-240/329-2-10). It’s a hyd flat used with the 465s from 1990-1994. It’s also the same cam used in the Bulldogs. They are the Crane H1 lobes that measure:
Intake lobe H 240/329
300* @ .0042
240* @ .050
148* @ .200
.559” lift @ 1.7

Exhaust lobe H 250/340
310* @ .0042
250* @ .050
158* @ .200
.578” lift @ 1.7
Bob

Mate you're fantastic.Can't thank you enough.

Told you so.. good day mate!