simple ac compressor wiring question
 

Here's the deal guys I'm getting to wiring up the compressor on my 92 fummins and - am bypassing the stock wiring because it was all messed up, anyways I'm putting a toggle switch to turn the compressor on and off and I'm hearing that you have to put a relay in and run the power threw the pressure switch and I should be good to go?

fuse - relay- low pressure switch - clutch, as long as the switch is a high/low switch, but im sure it is as that year only has one switch (that i know of).

Thanks, what size wire, fuse, and relay would you recomend?