Not .010, but .0001 or .0002.

The bolt can be tight, but still have a problem. You want to pull in and out
on the  harmonic balancer. The play should be less that .006  I believe.
Try reving the engine to the same speed  neutral and see if the light still
comes on. It seems strange that it comes on only on light acceleration. I
would hook up a temporary oil pressure guage and see what it does.

Uh Uh...  Without turning the crank, about .001 oversize would be it and
only when that much wear has occurred and the crank remains true.

On all vehicles, the exhaust has to be dropped and on passenger cars,
the bellcrank has to be separated from the pin  then that whole assembly
(pin) removed so that the bellcrank/tie rods can be pushed aside to
allow the pan to be removed.  Starter also has to come out, oil dipstick
assy removed.

Once the pan is down, remove the oil pump and inspect it for clearance.

At this point, all bearing caps are exposed. IIRC, (I haven't done it
this way in some twenty years), I used to loosen all main bearing cap
screws to hand tight then remove on cap at a time inspect the crank
surface then replace the cap and tighten to hand tight.  If all the
surfaces look OK (No deep groves, etc.), repeat the process replacing a
set of bearings one journal at a time. The hardest bearing is usually
the front since it serves as the thrust bearing as well and is my
starting point.  

With regard to bearing condition, I have often seem some worn to the
copper layer.  If the wear is even, this is not of much concern.

Lastly, when removing the rear bearing cap, it should be dry as a bone
to the rear of the seal.  In all of my experience, I have only seen a
couple of rear main seal failures on a Studebaker.  However, it is
imperative that the seal also be replaced.

JT