im new here but im reading lots that says the 39 is a pita of a car however there is people that make conversion kits ive seen a couple that are under $250 for just brackets then u buy ur gm (blah) calipers... lots of different options out there though check out scarebird rustyhope plydo
theres a few others but i dont have the info at the moment.. here is a good article i found today...

http://www.webrodder.com/article.php?AID=52&SID=16&CID=

hope i helped a little.. as i have a lot of work to do on my 39 plymouth...

rob in tacoma