In a '73 it should be a 1600 Dual port. Dual carb is a common and pretty cheap conversion. I would have done it to my '74 but the left side carb would not have fit with the autostick shift solenoid being right there..
The blower housing looks stock, just painted white and not black. I don't think the engine has had much work done to it. Usually the common upgrade is a degree indexed crank pulley. Makes it easier to time them