Hey BarnOwlLover,
re "the XP-82 was recorded as being longer than the P-82B by a foot depending on sources."
It might help if you post the lengths you are asking about (if you have them). Sometimes errors were made in recording various dimensions, just as there were errors in performance numbers.
I realize that none of the following is for the XP-82 or P-82B, but maybe it will help sort something out. These are the different lengths I have found for the P-82E/F/G and the F-82x (unknown letter). All of them are from official sources of one type or another.
39' 9.115"_P-82E (this is probably correct as I believe it is from the Erection & Maintenance Manual) Note that the STA 0 (station 0) is 8.965" behind the tip of the propeller spinner and 39' 0.15" from the aft end of the fuselage. See the 3-view with dims below.
39' 1.32"__F-82E (from "Encyclopedia of US Air Force Aircraft and Missile Systems Vol 1, Post World War II fighters 1945-1973" published by the Office of Air Force History)
39' 0"____ F-82E (PHOI manual - numbers are sometimes kind of approximate in the PHOI manuals)
38' 3"____ F-82x (NACA tests in 1953)
39' 5"____ P-82F and G ("including nacelle" according to the PHOI manual) This is almost certainly incorrect as the tip of the radar pod stuck out in front of the propeller spinners by a noticeable distance - unless it is not the 'standard' radar nacelle?
The F and G models were based on the E model so the overall lengths should be greater than 39' 9.115"???
42' 3"____ F-82F and G (from "Encyclopedia of US Air Force Aircraft and Missile Systems Vol 1, Post World War II fighters 1945-1973" published by the Office of Air Force History) From tip of the 'standard' radar nacelle to the aft end of fuselage.
P-82E 3-view&dims