@GTs58, as I mentioned both these frames are marked with a CJ serial number so in theory they were made the same month/year. You're right about the shell though, it appears to simply be a slice of larger tubing.
I'm so curious (how curious?), that I'm going to take a 50 mile drive this morning to pick up a stripped down Cool Lemon SS frame I've been watching on FB Marketplace just to see what hides on it's underside. It also has a three piece bottom bracket adapter I want and I've talked them down to $20 so the cost is mostly in time/fuel. Thanks for your support!