Troglodyte and bigtruck guy are more my thinking. I would definitely use the plasma cutter before messing with the hole saw,if you have access to one. you can make a guide to make the circle perfect, if you are willing to drill 50 1/8' holes and clean up with a file it sounds like maybe it doesn't need ot be perfect, in that case you could freehand the cut (draw a circle and trace it with the plasma cutter without using a guide) and get pretty close. I have done that. I love the plasma cutter.

if you can get c-4 and det cord why waste time working on hotrods!! seriously, blowing stuff up has got to be one of the funnest jobs on the planet.

Oh, and if you use the plasma cutter you don't need a pilot hole. put the tip inside the circle facing to the side and tip it over slow, it will cut in and then you can run it to the edge of the circle and start your cut (I hope I explained that right).

Red