my '81 was burning oil but still had good compression and I was a bit baffled by this.  When I pulled the head and popped a piston out I found the compression rings to be good but the oil rings were carboned up bad.  I knocked the carbon loose and the oil rings seemed good then too.  I allready had new rings and bearings so I just replaced them.  I wish I had just slowly dumped a couple of quarts of ATF down the throat and I might not have had to rering it at all.