Here's what I've got so far.

I live in Southern Illinois very close to TransAM. A friend who wants to try loaded touring and I are going to drive over to Farmington MO and ride a loop to Springfield and Back. I'm planning on taking Route 66 one way and TransAM the next way. I haven't got exact mileage yet but I think it's going to be about 450 miles. We've got 6 days.

My current thinking is to go West on TransAM and East on Route 66. I think the Northeastern direction on route66 would be good for wind. But ultimately I doubt it would matter. It looks like Ozarks will be the big challenge on this ride with some strong hills.

75 miles a day through that country is a challenge for loaded (unsupported) touring. If you practice 100 miles a day for a few months before hand, you'll probably do okay.

For your 1st time, try starting with 30-40 miles per day as the target.

& you have a choice , enjoy the 6 days , and not worry about the daily, or be in pain every night
from pushing hard to meet a milage target.

Thanks but I think you misunderstand. I'm riding a bike, not hiking.

IME - the load doesn't make flat riding that much more difficult. But it can definitely take a toll in the hills. If you have experience riding hills unloaded, and have a sense of what distance is comfortable, reduce that by up to half depending on the load.

That said, remember that you're only cutting the hilly distance, so if you can do an unloaded century half of which is hilly, then you'd want to consider dropping to 75 miles when loaded. (50+25).

Of course this is only a very rough guideline, since we, the hills, and the load are all very different. Use it with more than a grain of salt until you have a sense of how you actually do riding with a load.