Alternator upgrades using a single drive belt are limited by the amount of power that can be transferred by the belt but using a serpentine belt considerably increases the possibilities. The kits include a set of serpentine pulleys to go over the crankshaft and water pump pulley and replace the alternator pulleys and come with a matching serpentine belt. They are sold for specific engine models only. The alternators need to be purchased separately. If you order an alternator with a kit it will come with the appropriate pulley pre-installed. Installation is relatively easy. The kit comes with two 40" K6 belts. Because these are widely available at auto parts stores we do not carry spares or other sizes. In the event that you need a different length belt you have to source this yourself. This kit requires an alternator with a K6 pulley
The Perkins 4107 and 4108 can have different mounting foot styles for the alternator. See the additional information tab for more details.