I believe oil temperatures hover around 180-220 degrees fahrenheit. I'm pretty sure oil viscosities are measures at 100 degrees celsius (212 F).
I wouldn't tap into the oil line simply because lowering the oil temperature is going to increase the viscosity of the oil. The coolant line setup would work well, but at the cost of added complexity.
I would just get an aluminum heater duct, route it from the front of your car, to the rear of the engine (touching the headers), and back to the throttle body. Your engine is reversed, but it should still be doable.
You could also create a
heat muff through a similar method, but instead leave the heat output angled towards the throttle body rather then directly attached...no need to create a throttle restriction.
- LostCause