555 Timer to drive IRFP460
You're can probably make this work. You will need to use to use a CMOS 555 and operate it from a voltage between 12-15 Vdc. You will also need to buffer the output with a complimentary pair of beefy transistors such as 2n4401 and 2n4403.

This buffer is extremely simple - feed both bases from the 555,both emitters feed the MOSFET.  The collector of the NPN transistor connects to the 555 V+12 pin, the collector of the PNP transistor connects to ground. 

You may need to add a low-value resistor in series with the gate of the MOSFET to reduce the chance of parasitic oscillation. Start with 10 Ohms and physically place the resistor as close to the MOSFET as possible. 

This should give you very fast edges at the gate of the MOSFET.