Capacitor and inductor math problem

I'm trying to create a 400 amp inverter welding machine, and may require 4 aluminum electrolytic capacitors in parallel to provide the power(or whatever is needed). Main voltage is 120vdc. I need to know what size capacitor do I need and how large of mosfets do I need to get the job done? The reason for the mosfets is, in an inverter welder the capacitor bank is hooked up to a series of mosfets which are connected to a heatsink which the positive terminal of the welding machine is hooked up to. To my knowledge the metal plate on the back of the mosfet is connected to the drain pin which means its becomes a part of the circuit along with the heatsink that its attached to thus allowing current to flow to the terminal. I need someone to do the math involved in this operation to figure out how large of a capacitor I need along with the mosfet I also will use an inductor to increase the voltage to utilizer the full potential of the capacitors. I need someone to figure out the appropriate size inductor to use as well