Couple random thoughts
Patrick -
It looks like you have a great machine! It's not all rusted in some areas that can, at least in my mind, change a machine's personality. The edges of the cabinet are great looking, rust wise, and even the corner gussets look nice. Your machine, though dirty looking to you, is not really very dirty, especially not for one 40+ years old. I opened up 10 year old belt drives (a while ago!) that were far dirtier. For me at least that would be fun to clean up....
I thought about you yesterday as I was bringing back to life a 1980 built Kenmore standard capacity machine with straight vane agitator and water fall filter. It's the first water fall filter machine that I've used for myself since I was a kid. As I was working on mine (it hadn't been used in over 10 years) I wondered several times if you were doing the same with your new toy.
Regarding the two-way valve: I checked Sears online site. The valve is NLA, however if you are determined to restore this feature, I have a feeling there are ways to do that, either through used parts that undoubtedly are out there, or a NOS search using the internet. Don't let anyone tell you what you should do with your machine in that regard - that's up to you not anyone else. You'll need a facility to handle two separate drain hoses once the system is working correctly, so you may want to keep that in mine when making your considerations.
About the dull tub - There were bazillions of machines made with the white tub, in fact there are probably a dozen visible in pics of the farm. The trick is going to be to find one in nice shape. I believe, but don't quote me on this, that most machines, 70 series and up, had the white tubs in the 60s.
It may be that your tub has a lot of residue and dust on it - I had a machine that failed when full of wash water, and it was never rinsed. When I fixed it and ran clean water in it, it cleaned itself up. It started out gritty, dull and flat looking, after, it was pretty nice.
I have one restoration to work on this summer that will need a white basket as it currently has a much newer speckled version in it. If you decide to search for a tub and find more than one, please let me know, and I'll do the same.
Keep us posted Patrick!
Gordon