What is the cheapest easiest way to put a higher rear gear ratio in my SC300? (1992 model)

 

Cheapest? Buy an open diff with a ratio you prefer.

I personally was looking at the LS400 3.62 diff because it's cheap as dirt and should fit. (or so I have heard)

If your car is an manual with 4.08, you can pick up an auto 4.27 open diff for cheap.