It's much more likely that the valve guides have gotten gummed up with varnish from stale gasoline, rather than too-stiff springs. That usually happens after the initial startup, once the stale gas gets to the valve guides. The gas tank should have been cleaned thoroughly before any attempt at starting was done. If original pushrods can't be sourced, it's possible to fabricate new ones from thick wall seamless tubing, with the ends of the bent rods pressed into the tubes. It won't look original, but someone would have to pull a valve cover off to see what's been done. It's possible to straighten a bent pushrod, but I doubt if it would ever be as rigid as it was originally. Tubular pushrods are used in high RPM racing engines, and Comp Cams used to sell a kit to custom engine builders who could cut the tubing to the right length and press one end into place. I used to do that with the MOPAR pull truck engines I built. Now you'll need to remove all the valves, polish the stems, and ream any residue out of the guides.
Jerry
