Red Wire labelled as 'Common' in HVAC
This is indeed the standard R/W setup for a heat-only system.  You have it correct that you can attach the blue wire to the C terminal on the board and then use it as a C wire for your new thermostat.

If you want to make sure -- you can use a voltmeter to measure 24VAC between R and the Ground terminal between the fuse and the 6 pin connector.