if i'm reading this right, what you have is a 3 position switch (on,off,on)but you need a 4 position(off,on,on,on). I can't think of a way to wire what you want with a single 3 position switch. you can get a 4 position or run 2 switches. but i'm not an expert, so I could be wrong.

'88 Raider. 2.6L dead...2.4L swap in progress, AT, 33's, 2 bouncy seat,AC, CC, 2.25 exh, 2" Tbar, 2" BL, rear DB, rear LSD,4.90's, SW hubs,gen2 uca's, KYB shocks, snorkel, elec fan, MSD.

'99 chev k3500 crewcab
'15 Subaru XV
'03 BMW i325