Get a switch and motor from a 70's to late 80's F-150 and two speed motor. I had to file down the shoulders of the motor and rubber bushings, but it was an easy enough mod. Many "how-to's" are out there and the switch and motor are readily available on eBay.
A Ford truck wiper delay switch F150 F250 F 150 Bronco 1989 with harness and and a 73 74 75 76 77 78 79 FORD F100 F150 F250 F350 BRONCO WIPER motor do the trick with the mods to the mounting pieces. Others may work also.