Hi Tim, 12019637 is normally used on slimline models and is physically smaller than a 651956 which is used on full size models. Not sure about a 755078.
Hi Ashfordkent, it’ll be the regulator. Should be C00229540 which is a Diamond ‘H’ 48ER101C1 twin circuit regulator. Original may be EGO brand regulator, conversion is straight forward.