I did some searching myself, and this is the best I've come up with so far:
https://bdew.net/pressure/infinite-water-source/
https://bdew.net/pressure/multiblock-tanks/However, I'd disable the recipe for the eponymous block from the mod (which is crazy overpowered), and any blocks that specifically require it as input/output. Looking on GitHub, it has a recipes.cfg, so I probably wouldn't even need CraftTweaker.
I've gotten conflicting results as to whether this mod will work with GregTech pipes: in creative mode, I was able to get the infinite water source and pump from the mod to fill a small boiler via small copper pipes (despite not visually connecting to them), but when I tried it in my survival world with a small boiler that was already running, it didn't.
Edit: connecting a wooden pipe after letting the boiler cool down reveals that steam is getting into the pipes, despite being below the boiler (the wooden pipe ignites immediately, though planks placed in the same position do not). I will file a bug.
To answer how it's possible to make a crop and rubber farm with opencomputers: the geolyzer can see adjacent block metadata. OC is really quite a powerful mod.
That's a neat trick, and not exactly easy to find in the OC documentation. However, after realizing I didn't really need to leave the roof of my charcoal pile in place, I came up with a different technique for populating it manually (with a little help from InvTweaks "auto-refill" option, so I guess not completely manual) that I find easier to deal with, so I'm less certain I want to bother installing OC.