Does this kit come with wiring, temp probe and pressure sender?
Yes this dual gauge included wire and both oil pressure and temp probes.
What is the max PSI in this instrument?
The PSI range for this instrument is 0-80 PSI.
Will this Westach gauge work without an electrical system in the plane?
No, this gauge requires voltage (8-30 volts) to operate.
Is it possible to order the 399S9-5/8 oil temp Sender separately?
Yes, this is part number 10-04540.