This may save you some time finding fasteners for your motor mount.
I used these parts and fasteners for the front and rear motor mounts on my '54 3104. I believe that they are as correct as I could find to the original fasteners.
+ item name
+ original GM part numbers and size
+ new Fastenal replacement number and sizes
+ original GM motor mount part numbers
+ Filling Station or Truck Shop replacement motor mount part number
FRONT MOUNT HARDWARE:> Shield - GM #3656502; Filling Station #TR-182
> Cushion Assembly - GM #3657520; Filling Station #CV-335A
> Plate - GM #3657522, used original plate that was on the truck
> Retainer - GM #368449, used the original retainer that was on the truck
> Middle Bolts (2) - GM furnished by engine plant; Fastenal #21879 7/16"-14 x 2-1/4" Zinc finish SAE J429 grade 5 round head carriage bolt
> Middle Washers (2) - GM #352282 7/16" ID, 13/16" OD, 0.062 thick; we used 3/8" stainless washers that are the correct OD and filed the hole to 7/16". the 7/16" washers that I bought were 15/16" OD and might touch the crossmember.
> Middle Nuts (2) - GM furnished by engine plant; Ace Hardware 7/16"-14 top lock nut.
> End Bolts (2) - GM #3701135 3/8"-24 x 1-7/8" carriage bolts; used the GM carriage bolts that were on the truck. If you need the end bolts, you could use Fastenal #0159808 3/8"-16 x 2" Zinc Finish SAE J429 Grade 5 Short Square Neck Round Head Carriage Bolt
> End Washers (2) - GM #365685 3/8" ID, 1-1/4" OD, 0.187 thick; Fastenal #11101273 3/8" x 1.250" x 0.125" Thick Zinc Finish Extra Heavy Fender Washer
> End Nuts (2) - GM #117212 3/8"-24 hex; Fastenal #37464 3/8"-24 Cadmium Finish Grade A Flexible Lock Nut
(Some references specified castle nuts and cotter pins, others specified for lock nuts.)
REAR MOUNT HARDWARE:> Upper Mounting Assy (2) - GM #3705444; The Truck Shop #54-07609
> Lower Mounting Assy (2) - GM #3705447; The Truck Shop #54-07610
> Bolt (2) - GM #3705450 1/2"-13 x 3-1/2; The Truck Shop #54-07611
> Bolt Lock (2) - GM #3717280; The Truck Shop #54-07612
> Assembly Manual part numbers & locations> 1954 Shop Manual "Motor Mountings" starts on p 6-13> Master Parts Catelog part numbers and descriptions 0.002 - 0.027 + illustration p. 95=========
Here is a Stovebolt post that recaps the installation of motor mounts in my '54. It includes the list of fasteners.
NOTE: I installed the two thick washers incorrectly. So disregard the photo of the underside of the crossmember.
> Installation of my motor mountsHere is a post by Denny Graham
describing the correct location of the two thick washers. Follow his info.
> The correct way to install the two thick washers- Lonnie
