I too wonder why your dad didn't get the chemo during his radiation. Terry is correct that it is usually the standard of care. Chemo along with the radiation just allows the radiation to work better and the dose is usually less.
If the oncologist is recommending chemo, I would certainly go along with it, particularly since you are unsure of what his stage was prior to the radiation. If they are still staging him at a stage II AFTER radiation, that would USUALLY mean that the tumor was larger and/or lymph nodes were involved prior to the radiation treatments. In any case, find out which chemo the onc is recommending.
I took the oral form of 5FU which is Xeloda both during radiation and for 5 months after the rad treatments. Most people tolerate the Xeloda better than the infused, but you have to remember that each person is different. With the Xeloda there is also no need for a port to be placed in the chest for infusions. I would also suggest finding out about any other chemo drugs the doctor is recommending. The other common drug would be oxaliplatin which can be very hard on patients and almost always causes neuropathy - which is generally long lasting (doesn't go away when treatment stops) or sometimes is even permanent. Your dad and his onc did to talk about whether or not the risk of the drug outweighs the benefit of it. Studies have shown that for a stage II it does not show any significant benefit (the oxi, not the 5FU) in relation to the risk. However, since the stage prior to surgery is in question, you will really have to talk with the onc about this.
Good luck.
Jaynee