So the 395 piston does indeed work with the 394. I removed the bottom ring since it is rather low on this piston, and sure why not. But I mainly did it to make installing the piston easier. On my first attempt, one of the rings actually popped into the intake as I was moving the cylinder down. I found with just the top ring and installing it with the cylinder turned about 30* off center until it cleared the intake and it was fine.
She should be all cured by today. I ended up with .030 squish after the install. At the stock .049 she had 165psi compression. So hopefully close to 175 now and a better burn pattern. I did a mild port job on her, gutted the exhaust, and added 5* of timing advance. We have 95 octane fuel here as standard, and cool weather year round, so I advance the timing on almost everything I can.