The Dirty Dingo Motorsports "Double-D" LS engine adapter plates are machined from 1050 High Carbon Steel and are designed as a true "bolt in" adapter plate for installing the 1997-2013 Gen III/IV LS series engine into 1958-72 GM cars and 2WD GM Trucks, and 1962 to 1991 Corvettes(Corvette 1958 to 1961 will require a frame stand to use a GM three bolt mount). These conversion plates will place your LS engine in the correct position when swapping from a small or big block Chevrolet engine to a LS series engine and have four different motor mount placement positions. The first set of holes position the LS engine in the original bell housing position, then 11/16" forward, then 1 11/16" forward, and the last set position the LS engine 2 1/4 inches forward from the original bell housing position. These are the most common engine positions for the major header manufacturers. No other conversion plates on the market are designed like these. Includes left and right adapter plates and all necessary grade-8 zinc coated hardware. These mounts are sold in pairs. These mounts will not clear low mount GTO rear alternator brace, but they will clear Camaro low mount alternators removing the rear brace. Will not fit on 1967-72 4X4 Chevrolet GMC trucks.