Okay, follow this logic:
-FujitsuTen makes the Isuzu stereo.
-FujitsuTen makes the most Toyota stereos.
-Toyota's interface for cd ('98 to '03) is the SAME as Isuzu.
-PIE makes an adapter for an AUX line in for Toyota (you have to remove the CD player).
-This adapter should work with Isuzu.
I will confirm this weekend as I bought one for my Toyota, but will try it on my Isuzu and let you guys know.
http://www.pie.net/sec12sb1p.htm
Nate