Yes each rocker should be recentered and adjusted so that the bore is parallel with the bed of the lathe. You make this adjustment with the small bolt that the arm rests on. This is really an easy process and takes very little time to set up and to cut out.  


















































 

After the cutting out is done, the real work starts. Make or buy whatever bushing you plan on using and press it in, I think I was 0.001" press fit and then ream out the bushing to size, I went to 0.001" to 0.0015" clearance. 
Oh, and I cut an oil groove in the center of each bushing, not very deep. You can see the rocker in the photo has a bushing installed and you can see how thin it is. I don't think you want to weaken the rocker by cutting much out, so be careful here. And don't forget the oil hole, drill and deburr it last.

One more thing, when you make the jig, mill the mounting post so the area that the rocker mounts to is parallel to the centerline, do this after welding. remember everything must be straight.  

some one in your aria must  have a valvgrinder,they have a attachment that does a great job refacing rockers. if  1 looses their corect  arc ,could be hard on the camshaft life. 
the inner bore on rockers is less critical, the brake hone will take high spots off. the critical  surface on the rocker  shaft is a must. buy a new shaft.
with the removal of spill tubes is critical 
drain holes  for splash oil going to front and rear  rocker and shaft as well camshaft life. lots of lube  is the key..
my present 292 y has 4years on it, never had to reset valves, dit gear  like new(recently removed the list gear like new.
running the engine with valve cover off is messy, but no leaks with covers on.