The bucket seats from a pickup or 4runner should bolt right in. I think the mounting points for them already exist in the cab. Haven't looked in a long time though.
At one point, there were "Wet Okole" (or however it's spelled) seats made for them, but I think the brackets were needed to put them in.

Hope this helps,

Todd

1986 Pickup extracab longbed "Woody edition"
SAS - 33's, 5.29's, lockright rear.

02 IS300 SportCross - my "DD"
94 2wd v6 extracab
04 Outback Wagon- wife's/family car