To give you more detail into what I did:

1) I told the Cruise line that I had a private flight out of Anchorage first thing in the morning. That way, they put me on the first bus out of there. (If I just said that I was picking up a car in Seeward, I probably wouldn't of gotten off the ship for at least 3 hours later as they disembark by priority of your flights, trips, etc. Local car rental people are the last off).

2) The bus ride was quick (much faster than the train and almost as scenic). It is about 120 miles. I swear, I was in Anchorage before I would even been allowed off the cruise ship normally.

3) I picked up the car and then drive immediately back down the turnagain arm (towards Seward). I went about half way and stopped and saw some of the sights there (like Portage Glacier and other attractions).

I arrived at Portage Glacier the same time that a number of people who were on my cruise ship that had taken the excursion that went from Seward to Portage Glacier to the Airport. (That happened because they left the cruise ship so much later than me) They paid something like $100 each person to do the tour. Mine came out much cheaper and I had the use of the car.

Yes, I probably took an extra 2 hours versus picking up the one way car rental in Seeward and droping off at Anchorage Airport. But, I saved three hundred dollars or so, so I figured that the 2 hours was worth it. (Actually, it didn't really cost me '2 hours' due to the fact that I wouldn't of been allowed off the ship that fast). So, net cost in time was zero. Net savings in $$$ was very high..