Oh, dear. Graflex Inc's (also predecessors' and successors') nomenclature confuses everyone.
Pacemaker Crown Graphics, often called Crown Graphics, and Pacemaker Speed Graphics, often called Speed Graphics, of the same size take the same metal lens boards. Older (before the Pacemakers) Speed Graphics take wooden lens boards and won't accept Pacemaker Graphics' metal boards.
4x5 Pacemaker boards are metal with a folded lip, are 3 23/32" x 3 21/32". Board sizes from Graphic Graflex Photography, 10th edition.
The Pacemaker Graphics' successor was the Super Graphic, offered only in 4x5. 4x5 Pacemaker Graphics will accept Super Graphic boards.