ferget toyota engines, they are cartoons infront of the mighty Mazda FE - its a torque monster - you then have to worry about breaking of the axles after the FE is put in.
btw this original engine is also very durable, you say that the exhaust valves were breaking, this leads to the conclusion that you were not using genuine parts and the mechanic was not adjusting the timing correctly - This can also happen if the head face is machined a lot, it then causes the camshaft timing to go off, The head is not supposed to be machined unless it is actually warped.
Most Pakistani mechanics are recommending machining to take a kickback from the machinist. It can work once or twice but not in the long run and eventually the owner gets bit like this.
