I get between 2 - 2.5 ohms on the primary circuit (which is what I found correct for 12v in Les andrews blue book). Be sure you disconnect the distributor before testing or it will blow out. I found this online---
In simple terms coils are rated by their primary resistance—less resistance in the primary windings of the coil allows more current to flow, which makes a stronger magnetic field. When the points open (or the electronic device that controls current flow shuts off) the magnetic field collapses and makes a spark in the secondary windings. It stands to reason that more current in the primary is a good thing, however the current flow is limited by the ability of the points, or the electronics in place, to handle it. Too little resistance means too much current flow, which can burn up points and damage electronic components.
For specific recommendations we contacted our pal, Don Lindfors, at PerTronix to get the straight story on coils. As he explains, PerTronix offers three oil-filled, canister-style coils and they are identified by the ignition system they are suited for:
The Flame Thrower 40,000V coils have internal resistance rated at 1.5 or 3.0 ohms. The 3.0-ohm coil should be used on PerTronix Ignitors installed on four- and six-cylinder engines while 1.5-ohm coils should be used for eight-cylinder applications. These coils can be used on virtually any inductive (non-capacitive discharge) ignition system.
Flame Thrower II coils have lower resistance, 0.6 ohms for use with Ignitor II ignition systems as well as many other high-energy ignitions. The low resistance helps to produce up to 45,000 V. This higher voltage allows larger spark plug gaps for added power and better fuel economy. Flame-Thrower III coils were developed for use with the new Ignitor III electronics. The extremely low resistance of 0.32 ohms results in 45,000 V and a coil that charges to peak, current typically 30-70 percent faster the other coils. It should be noted that these coils are compatible with Ignitor III electronics only.