My Valve Spring Compressor - Heads On/In Car
Whatever works when you got a welder you can make a lot of things... and that's what I love about a welder.
Remember that ProForm sells one too for shaft mounted rockers.
You can feed rope into the cylinder after putting it at TDC to keep the valve up... obviously leave some of the Rope hanging out the spark plug hole- don't push it all the way in, duh.