Saab "crab" style distributor cap (Bosch)

If you are planning to run a Volvo ignition/block mounted distributor with a 16v head you are going to need this cap to clear the thermostat housing.  The cap will clear the head but you will not be able to remove the distributor with the head mounted to the block. This means that when you assemble your motor, make sure that you not only put the distributor in first but that you install it in the correct spot.