hairline crack rear end housing

Hi members has anybody had this issue. i changed gear set from 323 to 391 on my dart . 83/4 721 case. I used a replacement rubber gasket and of course there was a slight leak. checked the bolts and retorqued to spec still dripped when parked. I removed the rubber gasket and was just going to use silicone and noticed a small hairline crack on the very bottom of the face of the housing.Has anybody tried to repair a crack like this with an epoxy and sand the area flat.I dont really want to remove the axle housing if i dont have to. I suppose i could grind out the crack and weld it and sand to. Any comments or experiences are welcome.