The block will have 22R stamped on the drivers side I believe.  Its on the lower back of block.  The head if it really is a 22r head will have a diff carb then a 20r intake would.  The 20r carbs are round.  If its a hybrid(20r head on 22r block) then the intake will look much diff as well.  You can Google 22r hybrid and see pics of it. 
If you really do have a 20r block and 22r head then I would swap the head back to a 20r.  I well built 20r engine revs well and has plenty of power. Just not as much torque as a 22r.