i know hunt's photo carries them if you're in mass but u can also mail order them from some companies.
there is a set of adaptors on this page that will work. http://www.cascademedia.net/cgi-bin/...de=stands.html
and this one does the trick for 10 bucks
1/4-20 to 5/8 Adapter with stop http://www.micsupply.com/standaccessories.htm
i prefer to use the ENG clamp from cascade and clamp to my stand. it has the correct threads on it and i can also clamp it to some sort of railing if i want to.
you can find that on the same page on the cascade site for 18.99.
hrob id love to check out your truck sometime if it would be possible. im located in boston. im currently a student and working part time as a FOH engineer. live recoding is a dream of mine tha hopefully will one day come true. shoot me an email if you have any onther questions about this stuff . firstname.lastname@example.org