Either way, you are going to have to remove it.
If you try the JB Weld option, make sure it is clean, dry and sanded down. Also be sure that all motor transmission mounts are in tip top shape.
I would try to call around your area and see who can weld cast aluminum before though, as well as maybe trying to find one to replace it with.
Just search for AX5 tail housing etc.
Be a good time to upgrade to a set of the above posters mounts IMHO.
And no, they are not known from cracking there as a rule.
1998 XJ on 37's.JK Rubi axles with chromo shafts and ctm's, 4:1 transfer case, etc etc etc.The Cherylkee....
2003 Range Rover HSE, 4.4 Quad Cam.
1998 Range Rover 4.6 HSE
2000 4.7 4WD WJ with a rebuilt motor.
4.3/700r4/new frame buildup (YJ)....
Years to gain the hands on experience, and offer it freely.
Minutes to gain the knowledge from the internet, and quote it just as freely.