Here's the tool you'll need for "head installed" valve spring removal:

www.ebay.com/itm/127446696906?

Either rig an air pressure adapter from an old spark plug shell and a quick connect air hose fitting to hold the valves closed with a manual transmission in high gear, or use two pairs of vise grips on the flex plate of an automatic trans, or pack the cylinder full of 1/4" nylon rope (20 feet or so) and turn the piston up against it. Be VERY careful not to drop a valve into a cylinder, or you'll definitely be pulling a head!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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