I would leave the gun alone unless there your needs/wants are very particular. If you have an exact configuration in mind go for it. Choose your smith choose your parts and do it but know going in that you will pay a lot more than an off the shelf configuration with an equivalent but not identical setup.
This is the reason so many people buy what I call production custom. Every manufacturer of 1911s offers features on a stock gun that you used to have to get a smith to do.
The SA mil spec is a good base gun but it will cost you almost what you paid for it to customize it. You have to ask is it worth it.
-The right to be left alone is the most comprehensive of rights, and the right most valued by free people.-Louis Brandeis
-Its a tool box... I don't care you put the tools in for the job that's all... -Sam from Ronin
-It is the mark of an educated mind to be able to entertain a thought without accepting it. -Aristotle