Hi and welcome to mightyram. All of the timing marks for the crank pulley are on the bottom half of the timing cover (either on the die cast cover on the G54B 2.6 engine or on the plastic cover on both the G63B 2.0 or the FI 4G64 2.4) facing upwards. A tip - once you have pointed your timing light down there and know that you're in factory specs you can tune these by feel (the timing light is more of a diagnostic tool that'll let you know if something is wrong with either the base timing or a fluctuation from an ignition fault). Under gap your plugs by 0.15mm, loosen the distributor nut with the engine running and maybe have a pair of extra hands on standby to keep your engine running @ 2000 rpm. Gently swing the distributor between retard/advance until you get a spike in rpm, back it off a tiny bit and lock it up. You should have an improvement in midrange power and some hidden performance across the rpm range.