No problem!
You are right -- there are a TON of SLT's in this world. I used to have one somewhere in my garage, and I see them at just about every garage sale I go to. Every SLT is in exactly the same condition - 'barely ridden'. Very few people ride these things, and very few ever have.
It's very interesting to think about, and I think that when Schwinn designed and sold the SLT they were trying to sell bikes to people that they knew wouldn't ride them, ever. I'm not a historian or Schwinn expert, but here's my understanding of what led to the rise of the SLT:
Bicycling was really, really popular in the 1970s. Almost everyone used a bike for recreation. People had 10 speeds, the stingray thing had happened, and both BMX and Mountain biking were born. Basically if you weren't doing cool shit on a bicycle you probably weren't cool at all.
Then, there were some events that caused the price of oil to skyrocket, and driving the family car became expensive. People started to use their bikes for recreation AND transportation. Riding a bicycle was no longer just for being cool and having fun.
But some people still weren't that into it. They didn't know anything about bikes except that they didn't want one. For some reason they got one anyways. Maybe it was because someone else gave them a bike. Maybe it was because they had a new years resolution. Maybe it was because they were lonely and saw a magazine ad that made them feel happy. It doesn't matter -- what matters is the final thing that motivated every one of those purchases -- The price! Every one of those people went to a bike shop and bought the cheapest "practical" bike the store had. That bike was the SLT.
They took the bike home and put it in their garage. They were going to use it when the weather got better or when gas went over $0.60/gallon, or if they ever had a hot date. But none of those things ever happened. The bike sat in their garage for 35 years, often with the price tag still on it. The SLT was a bike that people could buy without feeling like they were getting ripped off. It was a "good value", so even if you didn't ride it, you thought you could sell it in a year or two and get your money back.
There are different models, some better than others, but it was a HEAVY bike, a bike with limited gearing, cheap components, and crummy geometry. For your ride I think that geometry is the most important thing. the SLT geometry doesn't make the bike very stable when loaded. it puts your weight up high but it doesn't give a full 'upright' position, which would both be more comfortable and give you more control. Of the millions of bikes from the 1970s and early 1980s that you find for sale on craigslist, very few of them are ideal for long-distance touring. You can ride any bike across the country but if you are going to spend money spend it wisely.