You don't say if you are attempting to replace the clutch release lever with the bell housing still in the car or on a work bench. I have restored many bell housings, all of them on the workbench. Working on it in the car is difficult and you could get yourself into a bind.
Until such time that it is on a work bench another repair scheme is to drill the clevis pin hole out oversize and install an oversize clevis pin. They are available from Bratton's
The early levers have a small retaining pin with a woodruff key inside the lever. Once you get the pin out you have to force the lever off the end of the shaft. Sometimes that can be difficult. The later levers have a larger pin that is tapered and is driven in from the top. You have to drive them out from the bottom, which is usually not too difficult.
With the bell housing on a work bench you can remove the entire clutch release shaft which makes it easy to work on. You can remove the pins with a hammer and punch, a shop press, or drill them out from both ends.
More than likely you will find the shaft with steps worn in it and the two bushings in the bell housing shot. The pedal shaft is also usually found with wear steps in it. On the work bench is the perfect time to replace all the worn parts.
Tom Endy