I think this mod really needs a bit of added thinking to assure safety and prevent things from burning up.
To calculate resistor for LED Resistor:
RL = (70V - VF(diode) - VF(LED)) / IF(LED)
Assumptions:
Coil voltage really = 70V
Rectifier VF = 0.8V (typical for a lightly loaded 1N400x rectifier).
LED VF = 2.1V. Varies with LED color and specific LED manufacturer.
LED IF - assuming using typical value of 10mA
(70 - 0.8 - 2.1)/0.01 = 6710 ohms, closest standard value = 6.8K
Power dissipated by 6.8K resistor = (6800)(0.01)(0.01) = 0.68W (assuming 100% duty cycle).
A 1/2 watt resistor will burn up if left on too long. I try to never exceed 25% of rated power so you want a 5W resistor there. Wattage can be lower if you can *guarantee* the duty cycle is low (how long the LED is on / how long the LED is off). Even with a low duty cycle then you never want to go below a 100% load rating so you need a 1W resistor. But from a safety point of view - you should not assume anything other than a 100% duty cycle (e.g. shorted driver transistor).
If you use a 4.7K resistor (as shown in photo) -- LED IF will be 14mA. Might be OK but it depends on your specific LED. I try to never exceed 10mA for most LEDs.
Power dissipated by a 4.7K resistor = 0.94W! That puppy will be burning up if your solenoid voltage is really 70V and the LEDs were left energized.
So -- what is the typical period of time that the trolls are left hoisted up (hold voltage on coil)?
And can you guarantee to coil driving transistor will be shorted?