...'coz on Ronayers.com, it shows the same part number for the VTR.
I am not finding any for the Fireblades, but there is one available for the VTR....

 

I'm going to suggest PBlaster over any other penetrant. It smells like all hell but it works absolute wonders on deeply corrosion-locked stuff. Also, after the PBlaster has attacked the corrosion for at least an hour, up to overnight, hit it again and tap-tap-TAP with a wrench. Your goal should be to use vibration to drive the PBlaster into the threads.