There are some very specific differences on the 965 quarter panels vs 930 quarter panels. Can you use a 930 quarter panel and it will fit and look right -- YES. The front 930 weld on flares could also be used to make front 965 fenders. There are some areas you need to address. There is a hole and indent at the bottom of the front fender that the rocker panel attaches to. That needs to be put into the flared 964 front fender you are making. In the rear quarter panel there is an area where the old torsion bar hole is located that is different on the 964 and 965 quarters. If you can get those areas off a damaged 965 quarter panel it would allow a factory 965 rocker panel to mount just like a 965 car. Then you need a OEM turbo front bumper cover, and the 965 rear bumper ends that flare out to match there 965 quarter panel, the center section of the 964 is the same as the 965 center section.
If you keep your narrow body trailing arms it allows a RSR build of the rear wheel Speedline 3.6 preferable or a good copy RH to be built 11" but with 3.75 or 4.25" deep rear outer lip. On the front if you relocate the mounting points for the front suspension to get to turbo front end you need 8" front wheel as these mounting points move the suspension out 1" per side. Or leave them as they are and build 9's for the front vs 965 8" front wheels.
jdorociak@gmail.com jim I build/sell/restore Speedline wheels for my Porsche friends.