So, you're scaling this beast up to about 7kW?
I hope everything else can take it...
Note that you'll need to triple the supply voltage, and about triple its current capacity as well. (You still need an isolation transformer; line-op is not a good idea here.)
If you're keeping it at 1kW, then use a more efficient (read: low conduction AND switching loss, not just one or the other) part. Something 42N65 does not sound efficient, by either measure, here.
1kW at 136kHz could be done with a pair of TO-220, though I wouldn't really recommend it. You should have no problem using any cheap TO-247 part with modest ratings.
There is no need to ever use IRFPxxx parts. Today's MOSFETs are approximately 10 times better, in terms of all performance metrics (Rds(on), Rg, Qg, avalanche, etc.), and many are even cheaper now.
Tim