Putting a 4200 engine into a 3200 shell whould take an age and cost £££
The engine is larger and taller so you would also need a 4200 bonnet, and as such 4200 front bumper due to the different shapes, which in turn needs 4200 wings...as the 3200 wings are seamless into the roof you would need to change them too...in summary a whole new front end as well as a new wiring loom, new rear transmission, prop shaft, ECU's etc etc etc