I have an old 1960's built in oven model urj-40f. It works like a champ, but I need to update kitchen. I need to know the exact dimensions for this. Can anybody help

Almost any brand should be able to match the dimensions of the oven you have now because they all use standard dimensions. If you measure the opening and depth you can get a GE, or any other brand to fit exactly. The same is true of washers, dryers, stoves, and dishwashers. Normally, you will see appliances 30, 27, or 24 inches wide, and there are adjustments that are built in to make things like ovens and built-in dishwashers fit in the opening.