Hi Boc, good to hear another 89 running good.
I used a ND 2 wire 02 sensor, just clipped the original wiring and crimped it to the new 02 sensor, so far working great. I suggested this to Ray too. Around $35 where I get my parts. I also think manual hubs will help a bit in the mpg dept.
GL with your truck bro.

Erick

89 Malljero 4dr V6
94 Monstero SR (sold)
91 GVR4 turbo powa too many mods
83 300TD turbo diesel powa