Best is to draw your own plan and superimpose details from the purchased plan. Your parts determine so much of the build. I believe Mark Elliot and others have already written up how to lay out a stock but here's one way to work that is based on your parts and a bought plan.
Keep in mind:
Barrel diameter all along the profile will vary build to build.
Breech plug length will vary barrel to barrel
Distance from pan to sear will vary lock to lock
Trigger guards will vary in length of the bow
Buttplates vary in pitch and diameter.
Step 1. Trace the barrel. Get a long piece of brown shipping paper and lay your barrel on it. On the barrel make a mark that shows where the bore meets the breechplug. Trace the barrel to the paper and check dimensions of your tracing. Mark the centerline of the bore. Locate your touchhole accounting for if you are using a liner. Touch hole centered more or less on side flat, and enough room to clear the breechplug.
Step 2. Set the web or wood thickness between the barrel and the ramrod hole. If you have a swamped barrel draw a straight line between the bottom flat at the muzzle and the bottom flat at the breech. Now allow 1/8" to 3/16" for the web or wood under the barrel and above the ramrod channel. Cross hatch it or highlight it.
Step 3. Draw the ramrod. Cross hatch different design or highlight another color.
Step 4. Fit and trace the lock. Note where the sear bar is on your lock and mark that spot on the outside of the lockplate. Disassemble your lock and place the lockplate on your drawing, centering the pan on the touchhole fore and aft and the top of the pan close to the centerline of the barrel. Level the lock so the nose is centered in the web. You have some wiggle room here that can be very important in getting the lock set up so the nose is in the web and the lock tail centered more or less on the wrist. At this point without a bought plan you can draw an arc where the sear bar is, and an arc where the lock tail will end up.
Step 5. Locate the trigger. Lay your trigger plate on the plan and set it up so you have the leverage you want if a single trigger and the right setup if a set trigger. Draw trigger on plan.
Step 6. Locate butt plate. Know what pull and drop YOU want, not what the bought plan gives. Take your pull measurement and use this to measure back from trigger and lay out an arc that will locate the butt plate. Put your sights on the barrel and draw a line of sight that extends backwards to the butt plate area. Now set up your drop and you've located your buttplate.
Now you have your architecture set. Take your bought plan and superimpose the details. Slope of wrist, start of comb, shape of comb, shape and style of lock moldings, cheek piece, etc.
