Replacement for SZ-13866 in Peavey amp

Hello guys.
I have a Peavey Bandit for repair. Both power transistors have shorted. I had this peavey just a few weeks ago, with both drivers for these power transistors shorted, and an open SZ-13866 dual diode thats monted thru the heatsink. I replaced the driver transistors with the correct replacement parts according to Peavey, but I couldn't find a corresponding diode, so I used a 1N4007 and it worked. Now with this Bandit back on my desk, I suspect this 1N4007 does not behave so well once the heatsink gets hot.
Any idea what would a better diode?

Thanks in advance
 
Red LED. Unfortunately the package of a red LED does not fit the slot in the heatsink like the dual diode in DO41 package. A little work with a quill grinder and heat transfer glue may modify the heat sink. Use safety glasses when using power tools.