You'll need to put those shims back in and possibly need to add a little depending on the amount of "rake" the body has with the new axle. You can check the caster angle yourself by using an angle finder on the flat spring mount perch on the axle, which is exactly perpendicular to the kingpins. The spec for your '49 is 1 degree 15' to 2 degrees 15'. It won't hurt if your a little over these limits as longbox said, but you don't want to be under them.
Take a look at your shims, they should be marked as to how many degrees tilt they'll give. If they're between 1.5 and 3 degrees, I'll bet a dollar to a donut you'll be fine.
You can also check your toe-in yourself. Most guys chalk a line around the tires and measure carefully front to back. The spec is 1/16" to 3/16".
