Not surprising it's hotter at the back. Water flows through the block then turns upwards into the head, across the head to the t-stat housing. Along the way through the block there are holes between the head and block which allows some water to rise and exit, the holes are sized so most of the water stays in the block, they progressively get bigger as you go back. Water exiting the thermostat is what you want to check, that will be actual temperature. Depending on the amount of crude build up, it could be hotter then normal due to no thermo transfer, and less coolant. If it stays around 200 you will be OK till you get time to clean it properly with a rebuild. Block temps vary a lot due to the thickness of the iron and how it was cast, core plugs are good place to check, they are thin and touch coolant.
