Here are some more of the inside of my Gator when it was new. The baffle is at a very shallow angle, the first plate is butted up aganst it and the others get spaced according to the load in the pit, trial and error really.
There are captions under each photo but you will have to scrool down just a bit to see them.
You can make the plates your self. 1/4" plate seems to be standard and 8" wide will work fine. If they are too wide you loose something in the adjustment. The tuning plates rest on angle running along the front and back length of the pit and are full width. Also your baffle should be cut and welded so there are no gaps on the sides for flames to come through.