>      Then I got to thinking it might be tough to mark and saw
> the pins on the ends of a 60" board. I could obviously cut the
> tails on the top and bottom boards and then mark out the pins
> by laying the sides flat on the workbench and offering up
> the tailboards.But what about making the cuts accurately ..
> ..with the boards laid flat it would seem to be a pain to make
> cuts with the saw held vertically.Alternatively,to stand the board upright
> and make cuts at a 60" height would be awkward also.

I've done this with a couple of large carcases.  Like you, I'd concluded
that marking the pins from the tails was the easier way to proceed (and so
it proved).  However, I found that laying the sides flat on the bench didn't
work very well; the top had a tendency to wave around in the air and marking
in the space formed by the tail openings and the benchtop proved very
awkward.  I employed two cheating devices in order to help with the vertical
approach.

1) a small platform to stand on when sawing  pins with the sides held
vertical.  I actually borrowed a 2' by 4' platform from a local theater, but
obviously anything would do.  Incidentally, given that my bench is backed up
to a wall rather than freestanding, the easiest way to hold the sides
vertical proved to be with the vise, having first replaced the vise facings
with longer ones that extended past the end of the vise.

2) a right-angling device.  This was a jig essentially consisting of two 12"
wide pieces of plywood, as long as the carcase is deep, held at an exact
right angle with blocks and glued and screwed together.  You want the blocks
set in a few inches from the end of the jig to leave a place for clamps.
You can then use this device to hold the top and sides at a precise right
angle when marking.

It proved useful to make a support for the free end of the top just to take
weight off the jig.  I have one of those adjustable work rests, which I put
on the benchtop.

Hope this helps,
Tb.