That is a butchered 88/89 frame. Someone cut it up to accept an 87 swingarm. If you want to keep it an 89 frame, you will need to get an 88/89 swingarm or figure out a spacer. The 88/89 swingarm were solid all the way through on the pivot, didn't have the cut out like the arm you have there. If you go with an 86/87 frame you will need the bracket that fits in that notch. The bracket is the rear motor mount.
Also you will need foot pegs, or pro peg nerf bars. OEM pegs are not welded on like the frame you have there.