Oil pressure specification for 1987 Jeep wrangler?

The exact oil pressure specification for a 1987 Jeep Wrangler depends on the engine it has. The '87 Wrangler came with a few different engines (the 2.5L 4-cylinder being the most common, and possibly a 4.2L 6-cylinder). There's no single number.

You must consult your owner's manual for the correct specifications. This manual will give you the correct oil pressure range for your specific engine at idle and operating temperature.

Failing that, a reliable Jeep repair manual specific to your year and engine will also list this information. Online resources may offer some approximations, but they should not be considered definitive. Using incorrect oil pressure information could damage your engine.