So.....from the pics you don't have an external trans cooler, nor is the auxiliary trans cooler hooked up. And the engine oil cooler lines aren't hooked up, either.
If I was to buy a trans cooler this would be the one:
https://www.holley.com/products/cooling/oil_and_transmission_coolers/supercoolers/parts/70274
The factory outlet line from trans to the auxiliary cooler is a factory all steel line but is no longer available. The
factory line from auxiliary cooler to the external cooler, and the
factory line from external cooler back to the trans have a flexible rubber section in them. As I mentioned they might be flexible enough to attach to a aftermarket cooler with different port spacing.
The AC Delco factory style lines are the only ones that won't leak, the aftermarket factory style lines tend to be jumk.
Your other option is to get out your tubing bender. Or cut out the rubber section of the factory style lines and install a AN braided line section.
The 1677 cooler looks to be about the same size as the factory cooler, and after looking closer it appears the ports may be close to factory spacing.
Your desire to have steel lines is a good one. Rigid lines flow better and are less prone to leaks, but it ain't going to be easy getting all the correct bends.
And get your engine oil lines hooked up to the driver side auxiliary cooler fer' crying out loud.......