LS Accessory Drive Bracket - A/C, P/S & Alt Brackets - works with R4 compressor This bracket REQUIRES an installation kit for assembly (Part HLY21-1, HLY21-2, OR HLY21-3, see Fitment Guide attatched for the correct installation kit for your application).Holley is pleased to offer simple, clean, cost effective solutions that solve the accessory drive challenges encountered when swapping a GM LS engine into a muscle car, truck, hot rod or other vehicle. These brackets were designed to deliver a factory style appearance, correct belt alignment and factory stability. Holleys kits supply the required brackets and hardware needed for installation, but allow you to choose the source for supplemental accessories and components that are often already on the donor engine or host vehicle. Whether sourcing from the salvage yard, the local auto parts store, your GM parts dealer, or Holley, you pick the accessories that match your needs and budget!A Fitment And Required Components Guide helps you locate and source components and provides other notes and helpful hints. Three easy steps will get you going. Step one is to determine your belt alignment based on your crank pulley position on the engine you have. Step two is to choose the Holley accessory drive brackets that you need (A/C, Alt & P/S or both). Step three is to see which Holley installation kit your set-up requires to line up your accessories with your crank pulley position. An application specific installation kit (part # 21-1, 21-2, or 21-3) is REQUIRED for most applications. Features: The most cost effective LS bracket solution on the market! Universal brackets fit virtually all common LS engines regardless of water pump and harmonic balancer offsets reducing cost and complexity compared to competitive products Simple, dedicated installation kits allow easy fitment to Corvette, F-Body or Truck drive offsets Utilizes commonly available and affordable GM alternators, power steering pumps and A/C compressors A/C brackets position the compressor high above the cross-member but below the hood line for easy installation and great looks A/C brackets are also a bolt on solution to relocate A/C compressor on engines using a GM Corvette accessory drive system A/C bracket accepts GM R4 compressor (Sanden version now available) OEM quality natural finish die castings for clean looks and durability. Can be polished, coated, painted or plated. OEM spec flanged head hardware included to match your factory LS engine hardware Complete accessory drive kits include all components and accessories are also available Ideal for crate engines, take out motors and engine builders! DragPartsUSA.com offers Holley LS Accessory Drive Bracket-A/C, P/S & Alt Brackets-works with R4 compressor 20-131 at low everyda prices. Be sure to check out all of our products from Holley Performance Products including Holley Performance Products Chevy Serpentine Pulley Systems.