Seen MK5 bumper on a mk3 before, looked shite.
To be able to do the conversion properly with everything you will need, front inner wings, front wings, front panel, front slam panel, bumper, lights.
Then the doors will look out of place, so fit mk5 doors (different curve in them)
Then the rear quarters will look shite, so replace them with mk5 ones
Then the rear will look shite, so replace the rear bootlid, and light panels
IMO
Yes, do the MK4/5 Rear if you want to.
Other than that, sell your MK3 to somebody that wants a retro shaped car, and buy yourself a cheap MK5 and dump a puma engine in it
