Measure twice drill once...Need guidance.

[jtoolin73]

Hope every one is healthy out there.

So I was quite sure that I had these holes marked on center, where they needed to be drilled...
As you can see my measuring or drilling skills are lacking and my four holes are off by about 1/4 in.
These are/were pilot holes just to get an idea of gas tank position.
My dilemma here is that I need to drill even larger holes, 5/8" diameter in order to fit the bungs that need to be welded in there.
I can either line up the front holes and drill the back or vise versa. regardless the holes are off center of the drill and I don't know how i'm supposed to make a proper/centered hole, at the correct placement.
I did buy a drill guide block that I was sure was going to be my fix but it's too long to fit anywhere on the frame at the hole i need...
Hopefully the pics will help my lacking description...

Any good ideas on how to drill a proper hole???

 

[5twins]

I think I'd drill a very small hole next to your off big one then just grind and file to make a slotted hole.

 

[Ratranger]

Mark out the hole and use a carbide burr in a die grinder to make it. Or weld it up and redrill.

 

[jtoolin73]

I think I'd drill a very small hole next to your off big one then just grind and file to make a slotted hole.

I will contemplate on that, its not a bad idea.

 

[jtoolin73]

Mark out the hole and use a carbide burr in a die grinder to make it. Or weld it up and redrill.

filling and re-drilling was my first thought but still unsure.