Valve seal replacement

Thanks all for all the replies. Here is what I’ve decided. I will first try the air pressure method, but will divert to the rope thing if the engine tries to rotate. I’m not sure what to think about stuffing rope through the drool tubes……. Seems odd to me. Now, once I screw up and drop a valve I will pull the head. Here’s my next question, does anyone have a recommendation for a head porter? If I pull the head, I will want to pocket port and clean up the runners, increase valve size if possible, install hardened exhaust seats, check and replace the guides as needed, possibly mill for positive seals, and mill to get to 8.5-9.0 CR. The only porter I know of in Colorado is Colorado Cylinder Head, but the old guy who knew Mopars has retired I hear.
Thoughts?