These sound way too tight, but heres what my FSM lists the clearances as:

Main Bearings: .004-.022mm or .0002-.0009 inches

Rod Bearings: .020-.045mm or .0008-.0018 inches

Can anyone confirm that these numbers are wrong (or right)?

sounds about right.

most of those era nissan engines have extremely tight clearence.

hmm I couldn't find any plastigage locally that could measure down that small. The smallest I could find was the red (or blue, or green I forget, it out in the garage now) that went down to .002 inches