Installed on my 1965 Chevelle with Vortec 350 and GM serpentine belt system. Fit perfectly in the original fan shroud and with serpentine system I needed reverse rotation. To use with heavy-duty clutch you have to trim about 1/16 off the inner tabs for the clutch to fit. No big deal.
Derale Blade 17917 is solid, well build and fit perfect in the new fan clutch for my Jeep Wrangler JK 2008,
excellent cooling blade, replace the cheap plastic electric from factory, recommended as the best.