Stock 340 springs vs comp 901-16

If the valve job sunk the valves up into the heads, you may need to use shims to get the 901's to spec installed valve height to get to spec spring pressures. Install them and use something moderately precise to measure from the bottom of the retainer/top of spring to the bottom of the spring. (You don't need to be to the precision of .001" in this measurement.) Being within .010-.015" of the spec installed height is good for most uses, IMHO; +/- .015" is a pressure change of +/- 6lbs. Spec installed height is 1.650" IIRC.

I think I would use the rope trick to get them off of the 273. If you like, I bet your machine shop would check the springs for you, or let you use their spring tester, just to make sure you don't have a one going flat.

At .468"valve (with the spring at spec installed height when the valves are closed), your spring pressure is going to be around 260-270 lbs. That is pretty decent spring pressure without going into the range of 'high' pressures.