For comparative pictures, see http://tailspintopics.blogspot.com/2013/10/lockheed-pf-80.html
In summary, the P-80A did not originally an ejection seat. The P-80B and C did. The incorporation of the seat required that the windscreen be moved forward about eight to nine inches and the forward end of the canopy lengthened accordingly. However, the location the aft cockpit bulkhead, instrument panel, and flight controls did not change. The gun sight was moved forward along with the windscreen. With the C, a ballistic jettison of the canopy replaced the mechanical jettison mechanism, which added a "tail' to the end of the canopy; the mechanism was housed under a cover on the aft deck of the sliding canopy that also sealed off the cockpit from a pressurization standpoint. (Note, the antenna on the inside of the B/C canopy is not shown and the depiction of the canopy deck aft of the headrest is notional.)
Gerry Asher provided the best illustrations that I have of the P-80A canopy deck at the moment.
In some pictures of the P-80, notably those with the P-80B canopy as pictured here but also A's, there is a triangular gusset at the lower aft edge of the windscreen that overlaps the lower front corner of the sliding canopy.
Note that the B/C canopy slid almost straight aft, whereas the front of the A canopy was raised as it started to move aft. (This is a test P-80A with no gun sight.)
The P-80A inboard profile of the forward fuselage:
The small cockpit was made smaller by the incorporation of the ejection seat. However, the pilot was not moved as far forward as you might think because the bucket seat and armor plate were located somewhat forward of the aft cockpit bulkhead, whereas the ejection seat rails were added as far aft as possible.
Gerry Asher and Bob Esposito are my go-to guys on the P-80.
First rule in USAF aircraft is never trust the externals to define the model. Modifications in the form of Time Compliance Technical Orders (TCTOs) have a long history wth USAF aircraft, and the early P-80s display a variety of them - the pitot placement being one of them. It was on the vertical fin of the A & B models delivered off the production line; the chin-mounting began on the C - it was retrofitted to the A & B eventually.
P-80A-1s (44-84992 to 85336) had the landing light in the nose - which doubled as a "combat light" for night engagements (!)
P-80A-5s (44-85337 to 85491, then 45-8301 to 363) had the DF installation (black radome) in the nose.
P-80B (45-8478 to 8717) was delivered with ejection seats.
P-80C revised the canopy frame/cabin press configuration.
All the P-80As - through 44-85491, anyway - left the factory in gloss gray. You'll note this one's stripped to bare metal - obviously been in service a while - long enough for a few TCTOs to be done (including the pitot).
(Yes, the sliding canopy was tinted.)
To add to the potential confusion, many P-80As were not only retrofitted to the P-80C configuration (the major change presumably being the more powerful engine), including the incorporation of the ejection seat, but redesignated as P-80Cs while retaining the original P-80A serial. The photo-reconnaissance RF-80As converted from P-80As also did not have ejection seats originally but a similar retrofit was accomplished on some of them.
You're on your own with respect to other detail P-80 configuration changes like the wing tips (round versus square) and different drop tanks. (The Navy did shore-based catapult testing of its P-80 with the drop tanks installed and determined that it was not suitable for at-sea trials from a structural or performance standpoint.)
I was disappointed but not surprised to see that while the 1/72 Sword P-80A/B provides both the bucket and ejection seats, the windscreen is in the P-80B/C position and the sliding canopy is that of the P-80B.
Gerry Asher, Fox 3 Studios, sells 1/48 and 1/72 P-80 conversion kits and decals. This is his build of the 1/72 Airfix kit F-80C with his cockpit, canopy, etc.
He also sells many other conversion kits and decals for the Lockheed P-80/T-33/F-94 series as well as other jets of that era. Contact him for a list of his kits at email@example.com and also ask to be added to his email list.