'77 390 amx ?

I have a Motocross Action or Dirt Bike magazine , with a test on a 390 AMX that they say is officially a '77 model. I can't find any Husqvarna I.D sites that list frame and engine numbers for a '77 model 390 Auto, so does anyone on this forum have any information on one of these ? In Australia, we have a pre '78 class in our vintage racing, which I think is pretty much the same as a AHRMA historic (?) class and I think that a '77 390 Auto would be a really competitive bike to ride in the open class. I have a spare '77 CR390 frame and a '78 390 AMX motor and would like to build up a '77 390 AMX .

Which way are the shock mounts on your frames? I know the 77 cr's look like 78 frames but I think the steering head was 32 degrees and then in 78 they went to 29 degrees. My friends have Autos but I cant recall a 390 for 77. Here's a link for the Frame# and years that seems to be pretty accurate.
http://www.husqvarna-parts.com/page/page/3895714.htm

The top shock mounts on my '77 frames face upwards , like the '78 frames. On the '76 frames, these top shock mounts face downwards. The '77 CR 250 & CR 390 are the first Husky models with leading axle forks, as far as I am aware and the steering head angle seems steeper than earlier Huskys because they turn fairly well. The only other differences that I can see between the '77 & '78 frames , is that the '77 swingarm was made of much smaller size tube and the '77 had ball bearing steering head bearings (where the '78 had tapered rollers).

You are right about the Timken style bearings which was the change for the 78 Model year and the larger swingarm. Maybe they ran out of 360's in early 77 and started using 390's. Is your frame # after ML-22000 if so its an 78 and can still have ball bearings. The factory always gave the CR's the best stuff first and the leftovers to the WR's and Autos. My friends have some autos with ball bearing frames and some with the Timkens but some are 79's but not the new style for frame for 79 they have the OR style frame with the extra rail on the bottom. If I can get any more info I'll let you know.