So I don't know what kind of time I will have but I have a "plan" of attack.
It starts with pulling the pump out again and checking once again for outer arm marks.
If marks, I'll sand down that area, try again.
If not, then I will lube the entire arm, put it back in, start it for 5 sec, shut down, pull arm out very carefully, and hopefully there will be clearly missing lube. Sand that area.
If it works, great. If not.....well I'm not wasting more money on chains hoping for a slightly thinner one. And we know it can handle a double roller just fine. And there is no way the eccentric would make that much noise. With the pump being new well....
I have a few options.
Try to sand the whole chain side of the arm down, see if any difference.
Drill the fuel pump holes 1/16 left/oblong I think it's called, allowing it to slide to the right. Or just step them up one size in general. Allowing me to slide it a little further away from the chain.
Get a fuel pump with the chain notch. Not ideal as the cheapest one I can find online is 200$ before tax or shipping. Any cheaper are all solid arms. I can try to find a used one (or sitting on the shelf) locally, but not a high chance of that.
Edit- I can get the Carter m6270 for $185 on rockauto after tax and shipping, strangely the cheapest on there.
Electric fuel pump swap, again not ideal , not cheap (unless I get lucky) and for sure some extra work. Plus I shouldn't have to, I would rather stick with the mechanicals.
I'll update as things progress.