There’s a lot on this site including a pretty recent thread.
Cost is realistically $10-20k depending on parts used and people hired.
It’s not hard to spend $5-7k just to rebuild a 915 at a decent shop
Full disclosure, I have a converted 915 Carrera trans with lsd, axles and shifter in the classifieds for $10k. Let me know if I can help.
http://www.914world.com/bbs2/index.php?sho...=356133&hl=