I had the same dilema in my 74 K20,when the front shaft blew the u-joint at the pinion end,when plowing one day--..needing to get the truck fixed ASAP to finish my plowing route,I cared not if I half-assed it back together,I'd fix it "right" later!.
Well,all I ended up doing was drilling the bolt out with a 5/16" drill,(mine broke off halfway in the hole in the yoke too)--and went all the way through the yoke,and used a 5/16" bolt and a nut on the back of the yoke,rather than try drilling it and using E-Z outs, or tapping new threads,or swap on another yoke (I had two on other front axles,but didn't want to waste time,and hated to "F" up the pinion preload!)...
I drove it that way from 1995 until last year!..never "fixed" the yoke!..I'd say just drill it right out and use a bolt and a nut!..the bolt has to be the perfect length so it wont rub on the pinion seal--I just used a hacksaw to "shorten" it to the right length..I used a grade 5 bolt,all I had available..a grade 8 would have been better maybe,but I never hurt the one I put there!...I would not be afraid to do this again...