I know sweat soldering a ball valve is best, but will a "push-ft" compression "Viperlok" brand ball valve work?---My pipes are old copper, and have a few minor scratches and pits---I also noticed a seam running down one side of pipe. This water line runs out into garden, but valve is in the house. Original gate valve doesn't close all the way---It still trickles water. I'd like to install the compression valve next to the gate valve---Idea is not to half to solder. I'm worried that the seam or tiny pits might prevent a good seal.--- Any suggestions?

You shouldn't have any problem with that valve. Sand the piping where you wish to install the new valve before cutting to insure that the surface can be made smooth and clean.