Hi Knifeswitch, welcome to VK
As you so rightly stated, it isn't just about a raw, fixed resistance value. During the initial power up and warm up of the tubes, the ballast changes it's resistance to regulate the current flowing through the tubes. Were this mine I'd do one of two things;
#1, the most preferable, I'd find a new ballast. If your search around they can still be found, and the circuit will function as intended.
#2, the hard way, use a 12SA7, 12SK7, 12SQ7, 12J5, 35Z5, and 35L6, and eliminate the ballast altogether. The 35Z5 has a tap for the dial light, so you won't loose that. I realize this is a fairly involved modification for someone new to this, but trust me it works, I've done it a few times to not only eliminate the ballast, but also on so called "curtain burner" sets as well (sets with the heater's dropping resistance built into the AC line cord).