Looks like the nylon is good for petroleum products, but I'd probably give it another couple thou clearance for moisture swelling. The Delrin is down around 180 degrees like the Polyethylene I used, but is really tough ... didn't realize Turcite is basically the same thing ... that stuff is now used on the wear surfaces of machine tools.
I can see there is a lot to know when it comes to plastic material selection. Wonder if anyone makes an app to plug in requirements and show material options. Not for this project really, but would come in handy.
What surprises me about the OEM solution is not so much the use of a bearing, but the use of such a low quality bearing in what you would think is a critical component, in a very hostile environment. I've never looked at a 69 bearing, but they did make a change in 69 that continued right into the 80's. From the pictures I've seen the 69 and later style is all sealed up much better than the 68 bearing, but evidently not the same dimensions.
It's obvious the spring is there to preload the bearing, but the necessity for pre-load seems to only be a function of the type of bearing they used, not something necessary for the overall design ... doesn't look like the 69 and later bearing requires it.
Always interesting trying to reverse engineer the OEM designs, in this case it baffles me why they didn't just use a standard sealed ball bearing (other than they are almost impossible to find with a 1" bore and less than 2" OD), or a needle bearing with an inner race sleeve on the shaft, and a seal. I CAN see that their solution was affordable, a bearing and spring that cost pennies. But jeez, no seal to speak of? They did use some kind of rubberized goo that appears to have degraded in short order to cover the outside of the bearing.
And, from what I've seen of these old columns ... I'd bet in 90% of them the steering shaft is just spinning inside the inner race on both upper and lower bearings ... making it effectively a bushing. It was doing that on both upper and lower bearings on both my columns ... and they felt just fine from the steering wheel.
I enjoy this stuff ... I realize that vast majority of people don't care, but I'd sit in a bar and discuss something like this for an hour
