225 drinking lots of fuel?

Unless your gauge is wrong, that's looking like around 11 mpg. Back when I had a slant six, I was getting 14-15 mpg around town. The first thing I'd do is put gas in it and see if the gauge is accurate. At 3/4 of a tank, you should be putting around 10-11 gallons in it. The one I had seemed to read 14 of 16 gallons (assuming a stock tank) from Full to Empty, but I guess that could vary, too.