I've got two of the rubber lines with the brass block end off cars I've parted out. No vented bolt. You can have these for the cost of shipping. PM me your zip code for a total.
Mike
Here's one at Mancini. Can't find the one from O'Rielley, but I'm pretty sure that's where I got mine.
http://chucker54.stores.yahoo.net/axlevent.html