at some point in time im keen to do this conversion too (money and time are not on my side). but from the information ive gathered (from a couple of reputable body shops), there is not alot of work that needs to be done. ive been told all you need is a pair of the r33-r34 conversion fenders, r34 front bar/bonnet/headlights and the only real modification that needs doing is the brackets that hold the headlights to the car, i was also informed that you can, as you have mentioned, change the rad support to an r34 number and not fiddle with the hlight brackets, but i think just modding the headlight brackets would be alot easier.
In any case, if you do do the conversion let us know, keen to see what it looks like and how much effort is really involved.