When I flew this summer - July 4 - 8th - I flew on a 20 seat 738 with mid-cabin lab. Although both flights were full, I got upgraded on both directions (IAH-ANC). IAH-ANC was EUA'ed at 5 day window. ANC-IAH was EUA'ed at 24 hours before flight time.

You are likely better off on the 753 - and you are now off season. So I think a Plat has a real good chance on the 753. A 753 will have one stop from IAH to ANC via SEA. Are you sure it is a 73G versus a 738 for the 737. I think the nonstop is discontinued at the end of Sept.

Are you sure the 73G is CO rather than AS code share? No upgrades on AS metal.