Damon (also sent via email),
I got the FAA 337 form from Tom Carr of Cessna Pilots Association. Tom teaches the CPA Skymaster class and covers all of the different changes to the electrical system over the years.
When he was maintaining a Skymaster for a customer (in the 80's?) he got tired of debugging the Skymaster electrical system and got his local FSDO to approve changing over to the 400 series regulators. Since then he's given out his copies of the FAA 337 paperwork to anyone who asked.
I don’t exactly know how much this cost since I had lots of other things done one the plane at the same time – but I’m guessing it was something like 2 to 3 days of labor, plus several hundred dollars for the cost of the regulators and miscellaneous parts. I strongly recommend the EI Ammeter:
http://www.buy-ei.com/VA-1A.htm
I'm going to be traveling this week - going to RTC for recurrent training. When I get back, I'll get a copy of the paperwork & schematics from my mechanic and send them to you. If you're a CPA member, you can also communicate with Tom at:
tom.carr@cessna.org