Back in the days when car parts were expensive and labour was cheap, one common alleged solution was "reboring in the chassis". This involved removing head, pistons, and sump, then bolting a crude portable boring machine to the block, using adjustable clamps attached to the head studs. The results varied from poor to worse.
Achieving a decent reboring job (to a toolroom standard, approaching production line quality) required two things: a full-sized (at least a Cincinnati No. 3, but preferably bigger unless the engine had a rather low deck height) vertical mill in excellent condition, and a qualified and experienced A grade machinist. In reality commercial reboring jobs were done on well-worn mills by people who were "qualified by experience".
Gadge, relatively small precision boring heads are pretty cheap these days (I think mine cost a hundred and fifty-something dollars including half a dozen different carbide tipped boring bars) but it doesn't have the rigidity to hold center when the bore has worn both oval, and off-center. It is much the same as this:
http://www.ebay.com.au/itm/50MM-PRE...DefaultDomain_15&hash=item462a04e059To do the job properly takes a truly massive head, in a truly massive mill.
