I do swap engines, and never advocate for the mazyota swap, firstly - the RX7 -8 geometry is not designed to take such a long mill, Its designed to take a small (20 litre keg) sized engine and a massive transmission which lies between the two axles of the car.
Putting the long JZ makes it biased towards the front. and being so incredibly powerful it makes the wheels spin any time the clutch bites.