that is the way to go. just get them made. the old ones can more than likely get stretched a little and a little wear in the spring leafs over 50 years can do it. it may be simpler just to cut them off instead of struggling to take the nuts off. your not going to use them again. check the centre bolts in the springs while you are there
http://www.lmctruck.com/icatalog/cbe/full.aspx?Page=37
ron