hi.
You want to install a 3/4 inch bulkhead or 1" bulkhead? The hole for the bulkhead will be larger than the bulkhead's nominal size, and you will have to look it up.
Actually, first find out if your tank can be drilled. If the glass is tempered, forget it.
Second, Go buy the bulkhead fittings first. Then take the bulkhead to a hardware store and ask for proper size bit for those bulkhead. Not all 1" diameter bulkhead use same size bit. Always have bulkhead in your hand before you drill.