Pat,
Here is some info that I pulled off the net a few years back. Sorry about the formatting, the spreadsheet wont paste well into this window. Should get you reasonably close. What thermite said about the breech/bolt face. Use .750" for that delta. No pistol info, but here you go.
Ken
Brl Length (in) Brl Dia (in) Distance from Muzzle (in) Min Port Size (in) Max Port Size (in)
11.50 0.625 3.850 0.081 0.089
11.50 0.750 3.850 0.086 0.094
14.50 0.625 8.375 0.063 0.078
14.50 0.750 8.375 0.070 0.086
16.00 0.625 8.375 0.063 0.078
16.00 0.750 8.375 0.070 0.086
20.00 0.625 6.875 0.086 0.093
20.00 0.750 6.875 0.093 0.096
24.00 0.825 N/A 0.089 0.089
From the barrel torque shoulder where the barrel extension torques against, it's 6.75" for carbine, 8.75" for mid-length and 12.125" for rifle to the step at the rear of the gas block seat.
Breech face is 3/4" back from the torque shoulder.
Gas port is usually 0.275" to 0.295" forward of the rear step, depending on if there is a handguard cap in the design or not.
You should be able to figure everything else out from that...
(Info From AR15Barrels.com)