Back in 2000, when I had my head and cyls done by Ron Scrimsa at Racing Engine Services,
http://www.racingenginesvc.com/ I asked him who could undercut my tranny. he gave me the name "Murdoch's". I wrote it down in my notes and never looked at it since.
Turn's out to be Murdoch Racing Enterprises, claiming invention of the air shifter.
Here's their web site, seems they do specialize in transmissions for drag racers. That should include undercutting. Worth a call.
http://murdochracing.com/parts.htmhere's a paragraph lifted from the "About MRE" page:
"Racecuts, Procuts, Magnaflux inspection, heat treating, hardface gear dog welding, semi-autos and full autos are all transmission services first introduced by MRE. Today MRE is still the industry leader in high performance transmission modifications, handling everything from your basic street-strip undercuts to custom, one-off automatics for exotic applications."
That ought to do the trick.