I know this has been brought up before , but I had an idea ( I know ) and want to know if it makes any sense.
Doing an LA motor , using a stud kit for the mains , and I anticipated having to modify things around the oil pump to get the pump to sit flush on the cap.
Well , shortening the stud and the nut both will not be enough.
I put the stock main cap bolt in there , and that would need to have the head shortened for the pump to fit.
Additionally , the gap between the pump and the cap is not square.
I don't know if this is a result of the cap being cut with too much material removed form one side...........I think that is unlikely to be the whole problem ,....... the pump mounting flange being cut crooked , or a combination of the two.
I haven't measured anything yet , but the cap looks visually to be fairly even on each side.
I am considering making a spacer to lower the pump below the stud and nut , and cutting it at an angle to square up the mounting flange.
I need to pick up roughly .200 " total thickness and something on the order of .060 " difference to compensate for the angle that appears to be from one side of the mounting flange to the other.
I have access to a mill and should be able to whip up a piece that will work for me.
That and two gaskets seems like it would work on paper.
This is with a Melling HV pump.
I haven't checked the stock pump , but if the rotor section is thinner , I could try that too and maybe solve one of the issues I am looking at here.
Thoughts ?

When I have ran studs on both sides, I have machined the caps spot face down around 0.200" and shortened the stud to gain the clearance. The side without the pump overhanging, stayed as per normal.
I also surfaced the pump mounting face on the cap to make sure it was flat. I only had to take a few thousands off in my case.

You want to make a spacer to raise the oil pump? Have I got that right?

My main concern would be whether you're leaving enough material for location of the pump in to the cap.

Something that might be worth considering.....A spacer would also reduce the amount of shaft engagement in the pump. Think of it as an axle not fully engaging the splines in a spool. A HV pump will create more load.

Is the pump cover plate parallel to the pan rails?

This is one more reason why I love you guys !
LA360 , that is the perfect fix and I can square up the mounting boss at the same time.
Locomotion , I hadn't even considered pump engagement.
I was way over thinking this , and completely forgot to look for the easy fix.
So let it be written.....................so let it be done !