It's unlikely a 1998 Chevy truck cap will fit a 2008 Chevy truck. While Chevy trucks share some design similarities across model years, the bed dimensions and mounting points changed significantly between 1998 and 2008. The 2008 model likely has a different bed length and width, and the attachment points for the cap will almost certainly be incompatible.
You would need to verify the exact bed dimensions (length and width) of both the 1998 and 2008 trucks to confirm compatibility. Even if the dimensions seem close, the mounting system will likely prevent a proper fit.
