All main bearings looks very good except nr 3.
Stock bottom magnum engine with about 100k miles.
Should i worry or just put new bearings in it?

New bearings, and line hone to set the clearance.

How did the last set off bearings look?Did you change anything?

The ones pictured are the originals.

What's the crankshaft #3 main journal look like?

With 100K on it... put new bearings in

Well you may as well mic the crank for the heck of it.

Even thought lots of miles, I would still try and find the cause. Tight clearance, restricted oil passage, etc. If you can't definitively find something, for sure line bore it - and check rotational torque upon reassembly.

Crank is mint.
Had great oil pressure.
Dont have new bearings yet but if my math is correct bearing clearence will be way too little with new bearings. Check it throughly and the reason for the bearing to look like that is from several factors all beeing on the same side of tolerances making clearence too small.
I think/hope a linehone will fix it.

Great oil pressure wont see a {possible} restricted feed to that journal. Its not unheard of for the oil feed channels to have casting flash in them. Id run a reamer through that oil feed for sure. Along with measuring the bearing clearance on it as well. A line hone isn't a bad idea, but probably overkill, unless its going to be a race motor.

I would check the center main journal for run out Even .0003 can cause that center main bearing to look like that with stock, tight bearing clearances

is there an .001 bearing for it?What oil did you run?

What Cab said
Exactly what I was thinking Cab. Have the center journal checked for a high spot.

Main bores are out of round .0008. Crank is bent .0002 but perfect journals. Rods are also .0008 out of round but all rod bearings looks normal.
All oil passages are good.

It's hard to see in the pic but it looks like high mileage "fretting" to me. Make sure you have enough clearance and run it.
Doug

I would put a set of full groove main bearings and a set of race type rod bearings in it so they have more clearances like .0025+ on the rods and .003+ on the mains
I've had several stock production early 1970s 318 motors that had the #2 main journal out of round and bent .001+ which I ended up having to use scotch brtite on that main bearing to get additional clearnces so the motor would run. Looking back now I should have used a set of 340 full groove main bearings in them
Good luck on your deal

Rods have plenty of clearence as the rod bore is on the bigger side. Actually a bit too big.
Ill check main clearence with plasti gauge. I have never used it but i feel on this i need to.
Or just spend the $400 the machine shop wants to correct it all.
That includes cylinder hone also.

That'll be the best 400 dollars you can spend. The mains need a hone and the rods resized.