Those three pictures were of a friend's original '55 Speedster. That dash has now been copied (I think) onto four different cars - one was a scratch build and the other three have had their dashes re-glassed and new holes cut for the Pre-A gauges, lights and switches. Interestingly, none of those cars that I know of are in the USA! Pretty easy conversion if you're starting from scratch, and a bit more work if you have a 3-gauge and want a 2 gauge set-up. You become pretty good at fiberglassing stuff.
So again......if you want a dimensioned drawing of a 356-A (3-gauge) to know where stuff is supposed to go, you'll either have to do what I did or get someone who knows where to find an original A or a replica with a dash that you like to make a dimensioned drawing/photo for you to follow.