Of course each of us are unique, but in general, daily protein requirements range from 0.8g/kg to 1.25g/kg body weight. We need more protein as we age, however the main focus is to preserve lean body mass and ensure adequate calorie and nutrient intake. Here's an article from Harvard (although it refers to elderly which 68 is not elderly), but gives you a good idea of where we're heading and what we know with the current research.
In addition to adequate protein and calorie intake, physical activity is strongly encouraged in order to maintain a normal appetite and to facilitate muscle anabolism or maintenance.
There's a lot of evidence showing that reducing animal-based proteins and increasing plant-based proteins is beneficial for overall health. You don’t have to replace all of the meat in your diet with plant-based protein, however switching just one serving of red meat per day for poultry, fish, or plant-based protein can make a big difference.