front A backing plates vs newer
 

I've read the bolt pattern on the a is a little smaller than the later ones.


How much smaller .?


Also later plates square bolt pattern and I've read 3 3/8. ?

Re: front A backing plates vs newer
 

Are you asking about converting to hydraulic brakes using a post 1939 Ford front set up? I don't know it for a fact, but I always thought that no modifications were needed to mount the early hydraulic backing plates to the "A".

Re: front A backing plates vs newer
 

For hydraulic backing plates you need to oblong the 4 mounting holes because the bolt pattern is just a bit smaller on the early spindles. Don't remember the exact bolt pattern sizes but you only grind like 1/4 inch on each of the 4 holes tward the center of the backing plate
Alot more info over on the HAMB forums if you meed more

Re: front A backing plates vs newer
 

The attached photos show what Phil is describing, before and after. Some people actually fill the holes with a plug and redrill them.

You also need an adapter kit. The kit has 4 pieces (each side uses 2 pieces). The first piece looks like a piston ring and centers the backing plate on the spindle. The second spaces the bearing out to the correct position. Most suppliers should have this kit but go for a supplier you trust.

Note that my comments are for a US production passenger car, your Canadian truck may be different.

Charlie Stephens