10" drum or Kelsey-Hayes

Disc brakes are better without a doubt but whether you can convert for under $500 is debateable. As for trouble shooting the drum brakes....check to see that there is nothing on the lining of the LF brake shoes and the shoes are installed correctly (short lining in the front) They have to be clean and dry. If they are, it's most likely that something in the RF is not working correctly. Double check the adjustment (including the self adjusters) and that both pistons in the wheel cylinder are free. The only thing else I can think of is that the hard line on the right front may be partially plugged.