Do some measurements to make sure... Generally, as long as you're within-generation ('98 - '00; '01 - '04) buckets and 60/40's are directly swappable as is. I'm at least 80% confident you could simply bolt the '04 buckets into the '98.
TTORA forum is the best Toyota off-road club around. We are nation wide with chapters in most states. Come in and discuss Tacoma, 4Runner, Highlander, & TRD models.