Here is an illustration of the 20" Skyelander 650b, this is available with either a 1" threaded steerer for a quill stem or a 1" threadless steerer for an ahead stem.
For a height of 5' 3" we have estimated an inside leg measurement of 724mm (28.5") and a saddle height of 639mm. Based on these estimates the standover height of the bike is circa 4cm higher than your inside leg measurement, so there are options we can discuss, for example a sloping top tube instead of the horizontal shown, we can also increase the bottom bracket drop up to 1cm.
It will be worthwhile measuring your inside leg measurement - if it's longer than 28.5" than it's likely the saddle will need to be higher than that shown in the image. To do this 1. Get a book and stand with your back against the wall, 2. Place the book in between your legs as high as it will go, 3. Move away from the wall keeping the book against the wall and finally, 4. measure from the top of the book to the floor. It will also be useful to measure the saddle height (bottom bracket centre to the top of the saddle) on your current bike and compare it against the illustrations.
If you would like a specific illustration showing your current saddle height (measured from bottom bracket to top of saddle) or based on your inside leg measurement, then click here to send us your measurements in mm and the frame size(s) you are interested in and we will create it and email it to you.