timing a 1990 c/k 1500

Can anyone tell me how to adjust the timing on a 1990 k1500 with a 350 automatic? I replaced the distributor cap and wanted to make sure that the timing was correct. I can't find timing information anywhere - no stickers under the hood. I read in a few places that it can't be adjusted.

Can it be adjusted? If so, what does it need to be adjusted to? Do you adjust by moving the distributor?

Thanks for you help.

Mike

You will have to disconnect the timing connector...this will be a single wire connector located behind the relay/fuse cover on the firewall or under the glovebox...you are looking for a brown wire with a black tracer (just unplug the connector)
if I remember right, timing should be 0 degrees