http://www.dexteraxle.com/
has a great site for brake and bearing parts for their axles. They also have an online service manual section. As for tires
"Before mounting tires onto wheels make certain that the rim size
and contour is approved for the tire as shown in the Tire and Rim
Association Yearbook or the tire manufacturers catalog. Also
make sure the tire will carry the rated load. If the load is not
equal on all tires due to trailer weight distribution, use the tire
rated for the heaviest wheel position.
Note: The capacity rating molded into the sidewall of the tire is
not always the proper rating for the tire if used in a trailer
application. Use the following guideline:
1. LT and ST tires. Use the capacity rating molded into the
tire.
2. Passenger Car Tires. Use the capacity rating molded into
the tire sidewall divided by 1.10."