Summit and other retailers sell spline lug nuts and sockets. Here are some of their offerings...not sure how to determine proper size...maybe with a caliper? Also I'm seeing 6 spline, 8 spline....but not 9 spline... http://www.summitracing.com/search?keyword=spline%20lug%20socket&dds=1
Otherwise, I wonder if a universal socket with the collapsible pins maybe work?
I can't speak for quality...never used one and don't own one. But it popped into my head as an alternative...
Do you plan to re-use these? If no, another alternative is to just weld another nut to the top of each one and get 'em off...20 times could get a little old though...a socket that fits would be better...
Or, I'd probably try to just tackle 'em with vice grips...they look long enough to grab to crack loose...
