The answer is always going to be a compromise, so do bear that in mind. Work out the ideal stuff and you will find that:
the spec was changed 17 years ago
it is not readily available in the size or quantity you want,
but you can order a lorry load
with delivery in about 12 months
and you supply the crane to unload the lorry.
In practice, most model engineering designs are used for such a short time, under such small loads, etc, that unless you are building heart by-pass valves, or intergalactic rocket nozzles, the choice can be reduced to 'what can I get that size this week'.
But if you want a guide with a USA bias, try Machinery's Handbook. Added benefit – all sorts of other questions are also answered.
Cheers, Tim