Machined as in having the mating faces shaved so the inside is perfectly round when it goes together? There is a diff shop here that knows their stuff, but I don't know if they can do the machining depending on what needs done. I have not talked to them about the caps.
I have a 489 case with 3.55 gears and a solid spacer. It was clear powdercoated years ago and it started to rust under the clear + it was weeping oil in a few spots so I took it out and removed the clear. I was just going to bolt it back in until I saw the MW caps.
I know the ring gear teeth can shear off and the axle tubes will bend inward under heavy racing. I know a local guy who ran one forever in a first gen Cuda and it wasn't until his car became capable of pulling the front end off the track did he start to have issues making him go to a Dana 60.
When I did it I went to my engine builder with the empty chuck and the cap, he did the gross cut in the milling machine and the final cut in is rod cap grinder. At minimun do the left side, ring gear side, that side sees the higher loading.
