Thanks Al. I'll give it a try tonight. I was not aware that a thick cast iron top like this one could warp!! Maybe that's the cause?? I'll take a look.
I wouldn't suspect the saw top is warped, but it's possible.
What may be happening is that when/if you can get it properly positioned , it moves when you tighten down the bolts and loses the position. Your bolts may have flat washers, not good if they are deformed, or star washers which are better.
My understanding of your dilemma was that you can NOT get it aligned and insert all four bolts. You were wondering whether to elongate the holes to allow for more lateral adjustment. Assuming you've solved that problem....I donno? then getting it snugged down without losing the position is the next issue.
Where are you in the process?
BTW, if you have a flat sanding disc from years ago, it makes a nice plane, without projecting teeth, to use a straight edge against for alignment. If not, just make certain your straight edge is clearing the teeth and is flush against the plate of the blade. By having a longer reference in front and to the rear of the blade, rather than just the blade itself, your accuracy is greatly increased.