Late model seats are expesive,and seats that fit these trucks that are in good shape are like hens teeth.None around.
Seatcovers from vendors are 200-250,and so you're still in the same boat moneywise.Maybe a pair of buckets from a grandAm or something if you're not too tall.Your gonna have to build a seat bracket prolly.Or you could do what the PO did.
Mercury Brogham,or something