Will an EV-81 tube fit in a Border Patrol DAC?

Hello,   I would like to replace the stock EZ80 rectifier 

with an EZ81 rectifier in a Border Patrol  DAC but don’t 

know how to. There doesn’t appear to be enough room 

in the tube chassis to do so, since the 81 tube is 3/4 inch 

longer than the 80  

Any help would be greatly appreciated. 
thank you!