the holley system does work with the mid length headers. for there long tube you have to mod 1 tube on the pass side and there is a pdf you can download thats linked on the ls1tech thread.
http://ls1tech.com/forums/conversion...truturn-6.html
post 119
speed tech says there system works with no mods having to be made.
http://www.speedtechperformance.com/...rod/prd383.htm