NOTE : There were 2 different switches and linkages used in K45 and K5-A. Make sure yours looks like the photos. Also fitsK5 -A. This has the longer bow shaped flat spring which was an upgrade for the short spring that did not always stay in place.
VINTAGE Speed Control Plate for KitchenAid K45, K5-A, 4-C, 3-C, K4-B mixers
Vintage speed control lever and tilt lock for KitchenAid K45 mixers
VINTAGE Speed Control Knob for HOBART KitchenAid 3C and 4C Mixers
Kitchenaid Vintage KSM90 Stand Mixer OEM Genuine Lever Control Linkage Parts Lot