finding equivalent Power mosfet in HF tube welding machine

Hi everyone,

I'm new in this forum, my english is a bit bad but I'll try to explain my problem.

I dont have much experience in power electronics and
I have this mosfet: http://ixapps.ixys.com/Datasheet/DS99027B(IXFN38N100Q2).pdf ,

The thing is, this mosfet is obsolete right know and I have problems getting replacements, so I need a easy to find equivalent mosfet,

Mosfet came originally in a HF tube welding machine: some specs

First stage, 3 phase six pulse rectifier 380Vac
Final stage, 1 phase inverter, Output 500Vrms, switching frecuency 400kHz max.
The inverter stage have 6 blocks with mosfets-diodes connected back to back (see attached photo) they work in two stages wih two diferent firing pulses (see attached photo). Each block have 16 mosfets-diodes in parallel

Parallel diode is http://www.mouser.com/ds/2/205/96509-67416.pdf

This are the best matches I could find:
http://ixapps.ixys.com/datasheet/ds100306(ixfn44n100q3).pdf
http://www.mouser.com/ds/2/205/ixys_98520-342341.pdf

I'm fighting with switching times and Id / Vds characteristics, I cant find equivalent mosfet with good ones as original.

I'm studying this problem but I want to hear opinions from more experienced people .

Thanks for your help
block

firing pulses

output voltage waveform