Don't discount the possibility you are listening to an exhaust blow. The V8 is known to produce quite high pitched metallic sounding noises this way. At tickover, or not under load, you probably won't hear them.
There again, if you do have a metallic tick, or tap, in the engine, the most likely candidates are in the valve train. If you've had bad oil supply in the rocker chamber, then you may well have worn rocker(s) and or shafts. Going down, the pushrods are known to wear on their ends, sometimes to the point of popping out of the rocker. Down further and next up is the hydraulic cam follower, Known for wear causing it not to seal and no longer pump up, leaving the valve train loose as if you had too large a tappet clearance. But this noise is much more likely at very low revs, and especially on start up. Then the engine will sound like a bag of nails and then quickly quieten down. Finally there is the cam. Badly looked after V8's - ie oil changes ignored, are very likely to wear the cam lobes away. You are unlikely to notice until the process is very far advanced, so unlikely to be your noise.
So my best guess would be a rocker shaft and or rockers, or possibly a push rod. It'll be really difficult to find until it's really far gone, though. So unless you fancy playing hunt the tap round the engine, renewing great chunks as you go, I'd simply wait for it to announce itself properly.
No harm having a careful listen in case it is something in one of the ancilliaries - alternator (I'll get my coat), power steering pump etc And don't forget an exhaust tick!
Chris