The pin remove removes the pins holding the upper chain guide (pictures in gsxr's response). If you've removed the injectors, use the heat shields a socket and a long 6mm bolt. Set the socket open side towards the pin, put the bolt through the socket into the pin using enough washers so it doesn't bottom in the pin. Tighten the bolt. At some point the bolt will bottom. Remove the bolt and add washers. Lather rinse repeat until the pin comes free of the head.

To get the chain loose you remove the tensioner. Loosen by the big hex against the block/front cover, not by the smaller hex on the tensioner stem. I think the same 27mm deep socket for injectors works on the tensioner.

Use a flashlight into the crank pulley from about the 11 o'clock position. Spray brake parts cleaner first so you see a distinct pointer and timing marks rather than a cruddy mess. Maybe look at the crank pulley from below as you turn the engine so you see the timing marks embossed on the rubber damper for a better feel of what you're looking for from above.

Since alignment of the cam sprocket and cam tower marks is somewhat subjective, average a half dozen readings, give the engine two full turns between.

Sixto
87 300D