It could carry a Genie and four Falcons (AIM-4s) in it.
No sure of the exact dimensions but as the AIM-4F was @86″ long and the F-106 could carry six (of 4 plus a Genie or 4 plus a gun) then the approximate lenght would be around 5 metres.
I have often wondered if, with a little modification, whether it would be possible to replace the Falcon/ Genie combination with say Meteors or AIM-120’s. Swap out the radar for a modern AESA unit and perhaps replace the J-75 with a modern engine and you could have a pretty effective stand-off interceptor. Just a little day dreaming I think.