*THIS* looks like a good transistor, higher voltage too. Good for your higher voltage mode.
Here are the specs that matter...
Drain-Source Breakdown Voltage:.... 150 V........ (3X target)
Continuous Drain Current:.............. 50 A......... (10X target)
Maximum Operating Temperature:... +175 C...... (nothing should ever get this hot)
Package / Case:.......................... TO-3P....... (Fairly big)
Power Dissipation:........................ 250 W....... (realistic for the packaging it's in)
The TO-247 package is about the same size/power. That would mean
*THIS* one.
Specs...
Drain-Source Breakdown Voltage:..... 100 V.......... (2X target)
Continuous Drain Current:............... 56 A............ (More than 10X target)
Maximum Operating Temperature:.... +175 C......... (super hot sauce)
Package / Case:........................... TO-247........ (same size. :-/)
Power Dissipation:......................... 200 W......... (seems close, a tad low if anything :shrug
To compare, here is a picture of the three different transistors next to each other, so you can get a feel for how much better/bigger we are talking here. The order is TO-220, TO-3P, TO-247.