Swap the 6 inch rims for 7 inch. I did this to 5 inch Volvo rims in the eighties, ended up going with adding 2.25 inches to the outside and removing .25 from the inside. You can work out the offset. 7 inch is perfect for 205 tyres of 60 or 65 aspect ratio. No problems with the front, but the back needs some work to clear the guards. I took 205x60 from 5.5 inch 164 rims and but them on my 7 inch rimsand the difference in handling was HUGE. I managed to get a set of P1800 sports caps with chrome wheel nuts which is not a bad look.

Postive and negative offset are confusing terms because they have swapped meanings more than once. Negative use to mean makes your handling worse, but now it means harder on your bearings. Where I live, you can add 25mm to the track to a fwd, more for a rwd. Check what your laws say is allowed.
--
Three 164's, Two 144's, One 142 & a partridge in a pear tree.