It sounds like the 220 outlets are NEMA 6-15R, with "squinty eyes" instead of vertical slots.
I would look for a switch to gang the two phases together so you get the full ~30 amps on one 110 outlet. It's handy to keep things balanced if you have one heavy duty thing that draws lots of juice starting up.
If you have a kill-a-watt meter (libraries loan them out) see how close it holds 60 cycles under various loads.
If you are considering this for home standby power, consider it'll probably burn through a 5 gallon can of gas in well under eight hours.