With all due respect IMO there is no such thing as a generic "Hawken" if you want to do it right (with certain caveats). Again IMO I believe the best way is to makeake as close a copy of an original as possible and Don Stith's kits, while more expensive than the others, are all based directly off originals and not some one's interpretation.
As Rich noted above there are several periods of Hawken rifles, but even within these periods there can be some variations especially in the early period pre-1849. But even when Sam took over after Jake's death in 1849 and began making the quintessential half-stock in a more less generic style, there were variations.
Variations exit between various individual rifles and periods and include: line of comb from buttplate to where it joins the wrist, cheek pieces vary not only style: beaver tail, eastern long rifle "square" style (common on full-stock of all periods albeit even some full-stocks such as the late 1850's Kennett have a beaver tail, beaver tail's also vary quite a bit in shape and size as well as being paneled or unpaneled. Other variations include: Fore end length and position of the keys, buttplate shape/size and whether two piece handmade of later cast, triggerguards varied in size and shape as well as being hand forged or cast, barrels: straight, swamped, or tapered with tapered being by far the most common. Barrel lengths varied from 32" to 42" with 36-38" being common whether halfstock or fullstock and that's just a start when taking this journey of discovery. Elsewhere Don Stith generously offered his help and I would take it if at all possible. You'd probably learn more in a short while talking with him than reading all the books.
caveat 1: While I recommend Don Stith's kits as being the most accurate, there are those makers who can use the somewhat disparate parts as offered by Track, etc. to make a good copy - Herb, who posted above did this with his nice copy of the Bridger Hawken made by Sam.
caveat 2: There are a few VERY few makers who know Hawkens so well that they can make a Hawken that's right without making a copy of existing rifle. The late Tom Dawson was one and today I'd bet Louis Parker could as well along with Don Stith of course....