Instead of doing all the whittling on the bell housing, how about using a hydraulic throwout bearing that bolts to the center bearing retainer, and finding a 48-53 216 or 235 truck bell housing with the SM 420 bolt pattern? There would probably be less monkey motion to adapting the existing clutch pedal to operate a master cylinder than doing all the metal butchery on the bell for mechanical linkage.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!