Ernest Christley wrote:

Another way to skin this cat, that most likely won't help Steve, unless he want to make a new rail from scratch. ...

Probably no need to make a new rail anyway.  One of the first
"tricks" I was taught in Machine Tool 101 (36 years ago) was how
to repair a mis-placed hole.  I still have that machinist's clamp and 
it's still hard to see the repair. 

If the hole is too large to smooth out, it can be drilled out to the next
size for a pipe thread and tapped.  Make a plug with the outside
threaded to match. Screw it in until it won't go anymore (with
reasonable torque.)  Mill (or file) flush.  [If you really want it to look
spiffy, chamfer the hole, and mill the installed plug to about .010"
high of flush, then peen the edges of the plug into the chamfer; then
mill flush.]  Drill new hole and ream to correct size. 

Of course - depending on the complexity of the rail - it might still
be easier to make a new one than fix two holes.

Best Regards,
Dale R.