Assuming that a 400V cap have the sufficient voltage rating needed you should be fine. Having mixed leads length is a non issue, however you should insulate the leads between the capacitor body and the PCB for an example by sliding a teflon sleeve over them.
Best of Luck
Peter
PS theres some other capacitor options here
True Copper Cap
Jupiter Copper/Paper Capacitor
Best of Luck
Peter
PS theres some other capacitor options here
True Copper Cap
Jupiter Copper/Paper Capacitor