Originally Posted by AlanKHG

First off, a 22" frame is 56 cm, as 1 centimeter is 2.54 cm; Google also has a unit converter you can use if you don't feel like thinking. Therefore, your question is effectively null; try using that frame.

However, seat tube length and its related quantity standover height aren't alone the determinants of bike fit; top tube length is also significant. On most bikes, a 56 cm frame has a top tube length of about 54cm, but some 56cm frames have 56 cm top tubes, which you may find too large. Generally, it's good to test ride a bike, but if you're dealing with old 10 speeds, they're cheap enough that trial and error may be viable.

Standover height is determined by the combination of frame size and overall wheel diameter. Assuming similar tires, 700c would result in slightly reduced standover height, as well as bottom bracket clearance. This would only be by a few millimeters, however.