1995 Mustang GT 5.0 H0 How to set stock valves

You're right there's no adjustment at all - tighten to ~20lb-ft iirc. I think you could technically shim the pedestals if you don't have enough clearance, or buy longer pushrods if you have too much. Either way you should perform a basic check that your setup is correct. The pushrod should stop being able to be spun by hand 1/2 - 3/4 a turn before tightened-to-spec or you might need to make adjustments - shims or longer rods as mentioned.

You might consider replacing the original stamped steel - on completely stock rockers, stock pushrods, stock cam, etc., I found excessive lash and ticking and was worried I'd wiped a cam-lobe or something. Turns out the old stamped steel had warped / bent over the years. I now have some Crane 1.7's that opened up the breathing even with stock cam (running turbo so the stock cam works well) and eliminated all of the ticking - lash was perfect out-of-box with no shims. Even fit under the stock valve covers.