I stayed away from the GN rearend (8.5 GM 10-bolt) because the Ford 9" does not use C-clips. The Ford 9" is a bolt on axle set-up. Make friends at the track, guys who back half their cars need $$$$$ and they need freinds looking to buy their old stuff.
i ran a 12bolt with southside lift converison bars in my first regal,had to get 5in offset rims and rolled the lip to fit my tires in,this car im running the 8.5 gn rear with spool c-clip eliminators with big bearing axles,and a lpw girdle rear has held up to a couple of 9 second passes before i got it and is still ready for more