Wanting to run some interior lights on my 87 4runner and possibly a power inverter in the back. Would it be wise to install a capacitor with an inline fuse to ease the battery and alternator load? Nothing crazy regarding the lights but was thinking about the battery and alternator.

 

Why a capacitor?
Calculate power you need for lights,
Calculate power you need for inverter.
Find proper gage wire for inverter.
Find proper wires for each light.
Get fuse block with proper fuses for lights.
Get fuse block with proper fuse for inverter.
Connect fuse blocks to battery through proper "main" fuses.

 

RAD4Runner's suggestion is what I would do.

A very large capacity capacitor (which is what I think you are talking about) is usually used in high consumption car audio applications when brief moments need a ton of power such as very loud bass notes. In that application, the capacitor stores a bunch of energy until the audio amplifier needs it for those brief moments in music where a lot of power is needed.

Depending on what you are planning, you may need a higher rated alternator to keep up with the electrical demand, or may be not ,but your expected load needs to be calculated first.