You shouda put up a better pic of the res. Can it be cut down some how? They sure don't need much fluid capacity.
One complicated solution is to lower that master. Then build a reducing bellcrank. GM used one on power brake-only pickups(67-72). It is a vertical pivoting lever with a pivot at one end, a push-point in the middle, and a push-point at the other end.
Then you build this lever & pivot, then calulate how much lower to move the existing pivot hole in you clutch pedal. I can try to get a pic if you can't figure out what I mean
If you design the points correctly, the push length will be exactly what it is now, only the master can be mounted lower.