I too own the Viking Platinum 755Q machine and looked at putting it on a Grace frame. While the 755 is an excellent sewing/piecing machine, the throat size would be too small 8" to place on a frame. Your wife will love it at first, then realize the setup is not going to suit her long term. When quilting a queen or king size quilt on the frame, she'll only have 3" or 4" of space for quilting at the end of the quilt. And unless she has another machine for sewing, she'll really hate moving the machine on and off the frame.
Instead, I purchased a used 9" throat machine (Pfaff GrandQuilter) and frame with stitch regulator for use as a quilting machine only. After using this setup for a few months, I'm already planning to upgrade to an 18" machine.