Ok on my 51 truck ...I purchased a 2 speed electric wiper motor kit for a 50's Ford pickup the kit had motor, switch, harness, mounting plate ,whole 9 yards as shown .......
..on the back you will see it has the exact same coupler that is on the firewall ......
....this connector is virtually the exact same size and shape as the one for the vaccum motor. this connector was just a hair too big to fit inside the stock coupler on the firewall.
I thought ok no problem simply swap coupler..from Vac motor over to electric.....Yeah right!...different shaft diameter ..no dice!
so what i wound up doing was to Very Very carefully use a dremel tool to open up the stock firewall coupler couple thousanths of an inch just enough to get the connector to press fit into the stock coupler on the firewall ......
....then had a bit of unexpected suprise it just so happens the holes in the mounting plate exactly line up with the stock mounting holes in the firewall and stock coupler....How bout that..!!
Then it was a simple matter of locating the switch and running the wires to it and hooking everything up. and there you have it ...in less then 15 mins i had working 2 speed electric wipers. now before all this i took the underdash directional pulleys and cleaned and lubed them up whne i reinsatlled them i left the tension nut tiny bit loose so the cables will self adjust for cable stretch......Not that i will ever need to use the wipers .....as i live in PHX AZ...Rain ...What's That??....
Just last weekend at the Car show it TRIED to Rain....Tried ...but in Vain ....spit and sputtered and wound up just enough drops to dirty waterspot the windshield. 10 mins later all done and gone. had 100 or so cars there mostly full .....then 3 rain drops fell .....oh hell hit the lights they scattered like roaches!
It was funny as hell to watch all the other folks scrambling like mad racing to get out of there and get their ..precious sugar cars home ....15 mins later had bout 20 cars of us still left laughing at the attempt to rain. few people came back most were done for day.
the wipers on my truck are there and do work in unlikely event of actually needing them ... but mostly for formality rather then functionality.
Larry