Is there an IC that inverts DC==>AC at the resonant frequency of a tank connected to it? (~50V ~40A)
This is essentially what an oscillator using a "tuned tank"  inductor-capacitor does. 

Google Colpits, Hartley, LC resonant, Pierce, ... etc. 

Can be done with as little as a single active device - eg a bipolar transistor or a MOSFET or a thermionic valve or ... .

Circuits below can be implemented "in an IC" if desired, but, just using a transistor will often be enough. 

Tuned tank oscillator - many images, all with links

Good tutorial - Hartley Oscillator



Hartley Oscillators

Basic Hartley oscillators - varying grounding point.
 NB note that this is what AC sees - DC needs a blocking component to stop DC shorting. 



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Shunt fed Hartley:





Feedback coil based from here





Colpitts  from here



and again from here