Question regarding heavy flamer sizes

[FormelyKnownAsSmashyPants]

Hi all, looking at starting work on a couple of heavy flamer sternguard squads for my Salamanders but I don't like the nozels on the heavy flamers that come with the kit, having said that though the rest of the weapon looks amazing, anyway I was wondering if anybody here who is familiar with both the immolator and sternguard kits could tell me how close in size the heavy flamers that come with the immoltor are to those in the sternguard box. I wouldn't be using the whole weapon, simply replacing the nozzles of the sternguard heavy flamer with those from the immolator. Will they fit, or am I barking up the wrong tree so to speak? Thanks in advance.