no oil pressure

1989 E-350 with 460 engine with 46000 miles has no oil pressure at any rpm. Lifters had just started to click. Dropped the oil pan, screen is clear and the punp "feels" good. Just don't really see what the problem is. Is it possible for the oil cooler adapter to cause this problem? Thanks.

don't know if a 460 is the same distributor driven oil pump as a 302 but a manual should tell or call a ford dealer and talk to a service tech.

I would pull the distributor and look at the gear it may have a new type plastic gear which is stripped. If a steel gear their is a pin in the gear which may be sheared. Mark the distributor and don't move the motor so it can be easily reinstalled. A broken timing chain is also a problem area but the engine wouldn't be running.
Did you use a manual gage like this to be certain you don't have oil pressure.
http://www.autopart.com/tools/toolsmain/tool/T_2001.htm
Bad bearings will drop pressure to near zero. Check clearances on the pump.