Try reversing the leads of the meter to see if it shows "no resistance" no matter which way the leads are connected. Some of these PTO clutches feature a diode in the clutch wiring. The diode (if present) is to shunt high voltage "spikes" to ground. If a diode is part of the clutch, and the clutch is GOOD, you will read "no resistance" connecting the meter leads in one configuration, and when you switch the leads (polarity reversal), you will read the true Ohms value of the clutch coil windings. The Ohms value seen should be near the range of 2.4 Ohm and 2.9 Ohm. Anything much greater than 2.9 implies poor continuity through the windings. Anything much less than 2.4 implies "a short" to ground. If a diode is featured in the clutch, and the diode "shorts out", it will give the same Ohm reading (no resistance) as a shorted coil winding. Are you disconnecting the clutch wires from the chassis harness to access the terminals of the connector? Simply slipping the meter probes into the connector while it is still plugged to the chassis side harness will give a false reading.

***"sometimes when trying to reengage the PTO or engage the transmission it will kill the engine"*** Sounds like it may be related to a safety interlock switch, or a relay that is part of the safety interlock circuitry. Is your PTO hydraulic, controlled by a solenoid valve? If that is the case, a defective solenoid valve might be overheating to the point of "going open" or even "shorting out" after it has been energized for the 20 to 30 minutes of operation. But, sometimes relays can act up when they are overloaded by too much current draw when they get old, or, if the device they are controlling develops too much resistance or "shorts out". When the engine "kills", will the engine crank right back up? or does it act like the battery is weak or dead?

You need to go to the vintage/antique tractor web sites. I have given a link to a good one below. Here is a link that might be useful: Yesterday's Tractors

Does it only blow with running the pto? I had one with a stator that eventually shorted itself to ground permanently that started out that way. Un-hook the connector, run it and see what happens.