Some reading-
TheSamba- IRS Axles 101 - narrow
TheSamba.com- Narrowed & Adjustable Beams - The Good the Bad the Ugly
Look for the June '94 issue of Hot VW's for a full description of Bruce Tweddle's method of narrowing irs arms. I don't know if he was the first to do it, but it was the first time I'd heard it done. I've posted those pages in a thread here before but you'll have to find them yourself- I'm packing up to go 4wheeling with my oldest... Al