There are two pins holding the upper chain guide. One is also the upper attachment of the belt tensioner spring as in your picture, the other is right at the head/block parting line behind the engine vacuum pump fittings. The one you found has an extension, the other one is recessed. There are several ways to remove the pins: Use an extractor tool like this (my favorite) -



Or a slide hammer like this -



Or use many washers and a bolt to draw out the pins. I believe it's an M5x1 thread, same as the valve cover bolts, but use a stronger bolt than the valve cover bolts.

Don't worry about the chain. It will not disengage from the IP and crank sprockets while the head is off. Worst case is it will fall further than your fingers can reach. Use a hook to pull it up when the head is installed. Don't use a magnet. It might attract debris in the oil and accelerate wear. Likewise, don't use a magnet to remove the valve lifters. Same problem. Try a suction cup such as for grinding valves by hand when that was fashionable.

Sixto
87 300D