It's not going to match Irwin's level of ornate workmanship, but these are the basics:
Tiger was neck through with an elaborate "hippie sandwich" body of layers of different woods and brass binding. It was also ungodly heavy. You can read about some of the details here:
http://dozin.com/jers/jers/guitars/tiger/info.html
Some more detailed info, including schematics are here (Waldo also sells Garcia-style buffers many Deadheads rave about):
http://www.wald-electronics.com/tiger.html
You aren't going to replicate that without having masterful woodworking skills or paying someone lots and lots of money. So the compromise is to either modify an existing guitar, or create a less ornate version.
For a Warmoth, you start with a WGD body (perhaps maple) with a figured top that you like. Tiger's top is cocobolo, but it's not going to affect the sound if you pick something different.
If it's a Warmoth neck, a maple LP neck with ebony fingerboard would probably be closest.
Pickups would be Dimarzios - Tiger had an SDS-1 in the neck, and either Super Distortions (aka Dual Sounds) or Super II's in the middle and bridge. Jerry switched from Super Distortions to Super II's in 1982, so you have to decide which era's sound you want. The wiring needs to split the coils, as Jerry supposedly spent something like 90% of the time on the middle PU split (using the neck side coil).
Tiger also has a buffer and OBEL (On Board Effects Loop), which sent the full strength buffered signal out to his effects and back
before the volume control. This allowed him to bypass his effects from a switch on the guitar and control the volume post-effects. Whether or not you want OBEL, you will want a buffer of some kind to give you a clean low impedance output.
Tiger had brass hardware, but I'm not sure if anyone is currently making that stuff.
Tiger had elaborate inlays, and there are people who will do wonderful inlay work, but that would cost a bundle. The inexpensive option is to get Tiger-like inlay stickers from here:
http://stores.ebay.com/Jockomo-InlayStickers/_i.html?_nkw=garcia&submit=Search&_sid=639778940