I think there are a couple of issues at play here - is it worth it to fix it. Interesting question on two levels. I've stated my mathematical equation (used the same one when spending $900 to fix the AC on my Honda Civic, and it's still going 3 years later). However, the second factor is - do you need to fix it or will it hurt anything? It sounds like, IF yours has this issue, it may not even be worth worrying about. You can a) drive it and not worry about it, b) drive it and when it does let go, plan to replace the engine, or c) fix it now with either new heads or an engine. I'm somewhere between b and c. You might be at a.
If the truck is in good shape otherwise, I think mathematically it makes sense to fix vs replace.
I'm thinking I might pull the oil sensor and see if there is any sludge in that area or - if I can access it - the oil pickup. If so, that's an automatic engine replacement. If there isn't, it might be worth a gamble to replace the heads.
And even if the engine then blows, I can probably either re-use the heads or sell them. Or have the bottom end rebuilt and use them again.
Questions, questions. Lots to think about.
If I pay for the work to be done, I'm replacing the whole engine. I think the labor for replacing heads is about the same as the labor to replace the whole engine. If I just do it myself, then I might chance just the heads. Upside is I can get the heads that I want (706 heads).
Just have to be careful not to push the engine too hard for a while after that.