WIW All Original 74 Duster 360 4 Speed Car?

Not sure why you think the engine needs to be gone through just because it has 100k miles.

My opinion on value: 10k is low, 20k is on the high side. I put it at 15k +/- $1000.

If I bought it, I would drive and enjoy it as is, and make repairs as issues pop up.

I think it's the perfect color.