Callaham screws are 1 1/4" 31.75mm long which are just like the original screws used in the Pre-CBS guitars, Gotoh are 24mm and others are shorter or longer.
On some builds you can find that if you use a Callaham or Vintage bridge mounting screw that it comes out into the spring route at the back....what is going on!!
The short answer is that bodies differ and you need to take some measurements first.
Your body should be 44.5mm thick with a 15mm deep spring pocket, however some after market bodies thinner for example olders Squire bodies are 38mm thick. Or the spring route is greater than 15mm.
The spring pocket should be 15mm deep which on a 44.5mm thick body plus 3mm thick bridge plate leaves 32.5mm and don't forget that the two outer screws are backed off a touch and the middle 4 backed off more this leaves enough depth for the screws. It is tight but that is how they were and are made.
Before you mount your bridge you should make these measurements to confirm. When you mount your bridge fit one screw first (you should always wipe the screw on some bees wax or a dry soap bar first) and as you come to the end check the spring pocket. If it looks like a screw tip is pushing the wood out then read on.
If the tip of the screw looks like it may push out then fit the screws to a safe distance then withdraw them and nip the end off and re fit checking the spring route.
This may seem like a bit of a "faf" but unless you are building from scratch as factories do and can precisely control the dimensions then these measurements are necessary.
You should not take the suppliers word for it that a body and all dimensions are "Vintage Correct". Don't forget that Fender made bodies by hand and there were variations and they made adjustments as needed.
