I thought I posted a response to this yesterday, but when I looked, there was nothing. I hate the home computer.
If memory serves me correctly, the guys that were making them were out of the Georgia Mtns and operating under the name "Thunder Road". I think they have disappeared, but let me dig through some old e-mails and see if I can get you a contact.
As for the Featherbed frames, they can hold just about anything there is a lot of room and clearance hence the popularity with a lot of the older cafe racers. I am toying with getting one and dropping a 1200 HD engine in it. You can find old featherbeds on CL or E-bay from time to time, and the 650 savage, should be an easy pick up. I would guess you can get an engine out of a wrecked one pretty cheap, and you can get the whole bike for 2-3000 on any given day.
From memory on the snorton, they worked the tranmission, and changed the drive from belt to chain and did a few performance upgrades to get a few extra horses.
A lot of folks make very high quality NEW featherbeds (unity equipe, manxman, etc) with MSO's. I would not say it is too far out of range to make it yourself or get a good one fabbed up.
The part I fould really funny, the guys at thunder road used tach and speedo from JC whitney. I had a good laugh on that because it was so simple.