Well, you will be on the young side for your age group. You aren't in an area noted for its' road cycling. The distances are pretty short. As has been posted it depends a lot on who else is in that age group. There are always a few people around who have been genetically the fastest since high school. If you happen to have one or two of those in your bracket you aren't going to win. On the other hand you many have people who are just out for fun once a year and you can't lose. Big thing is to not take it too seriously although there will be some who do.

Frankly, I wouldn't train as an athlete. I'd just make sure I was as fit as I can be for that day and go out to have fun. As for being too heavy; it all depends on your body type and fitness. I know many people who at your age, height and weight do just fine and some who are 30 years younger who are winners.

Remember, the Senior Games was designed as a marketing effort for a corporation and to encourage the couch potatoes to get out and do something, anything. The events schedule illustrates that. And, who knows, there may only be three competitors in your age bracket so you all get a medal!