I had a 1968 911L I should have converted to electric drive. However, a co-worker badgered me for years until I sold it to him.
If I was going to do a conversion of a 911 I would use the HPEVS.com AC-35x2 Motor and Curtis controller. I would keep the 5 speed transaxle and simply use an adapter plate and coupler and keep the clutch. This system is a low voltage system 144 volts and is much safer for a DYI person to work with. I would use 48-50 CALB 180 AmpHr LiFePo4 cells. These are the safest chemistry you can use and do not require active thermal management.
What you would have would be a 90-100 mile range car in the 3000lb weight class with 168hp and 188 ft-lb from 0-5000 rpm. This would make for a fast little 911. It would have programable regenerative breaking and you can even add a pressure switch on the brakes to add re-generation that increases as you press the brake pedal...
You can buy almost every part you would need off the shelf except for the battery boxes. Total EV drive line cost would be about $25,000 with the batteries....