I haven't been on here for quite a while, but remember reading a thread about modifying the ST400. But as I didn't have one at the time it didn't concern me, but was an interesting read. I've since acquired one, a '65. Could someone please post a link to any threads on modification? I'd really appreciate it and thanks in advance.
http://www.buickperformanceclub.com/SPTrans.htm - this is probably what your looking for. Written by Mark DeConti, he knows his stuff.