Echoing what PK said -- you should have a dialog with Brad when you order yours, and tell him the sound you are after and how faithfully you want to emulate Garcia's tone. He can build you a version that is 100% Jerry, but that will also limit the range of the SMS a bit, so you may want something that will give you more than just that tone. Here are his suggestions for mine, quoted verbatim:
I have a few thoughts on the preamp. Unless you're going for the authentic Garcia tone only replication, there is a variant on the preamp that I think sounds easily as good and is actually more versatile in general. It'll definitely get you a killer Jerry tone with the knobs set right, but it will also give you a lot more universal usage.
I'd recommend this version for you, and if you order please remind me of these details in an email.
Takman Carbon-Film plate resistors
Silmic II (silk/hemp) cathode bypass capacitors
This is pretty much my personal favorite setup for the preamp. It's very sweet and warm and the tone-stack voicing will cover all ranges and not lock you into just the Jerry-only setting as much.
I am very, very happy with this setup, and I love the warmth the above components give me. Your mileage may vary, as they say, but the above is working well for me.