1963 most place I know were wtill plastering walls.

In some markets a thinner than 1/2" base gypsum board had either a one coat of two coat plaster finish. Today USG calls it a Veneer Plaster System but contractors often call it "blueboard".

No plaster finish...just plain old sheetrock. There must have been another dimension of 1/2" back then was not really 1/2" (like a 2X4 not really measuring 2X4).

Our home is about 1966 and all the walls were done in 3/8". To get this flush, you will have to use 3/8" with enough shimming in back to make it level. A problem with this is that 3/8" is too flimsy for ceilings, but if your piece is small you should be OK. If the repair piece is big, try to insert backing plywood strips that span the repair piece and existing ceiling. (See link below). This will stiffen the repair.

Here is a link that might be useful: Drywall Repair

Thanks drywall guy...regarding the link....is it better to tape the joints? The steps just used compound.

For small holes you don't have to tape. For bigger holes or holes that are on the edge of a sheet you should tape. And you can always tape if you want - it might make it easier to cover the cracks.