Very interesting! A few thoughts...
- The MX-number is the Air Force's project number; there may be various contractor's project numbers attached to it.
- The Bell report number references D159; we already know that D159 was the Bell project number assigned in response to contract(s) issued under the Air Force MX project. Other Bell reports referenced include:
Detailed Specification D159-947-001
Aircraft Design (Includes all detailed drawings) D159-945-004
Preliminary Stress Analysis D159-941-001
Estimated Weight and Balance D159-942-001
Aerodynamic Criteria and Design D159-976-001
Performance D159-978-002
Stability and Control D159-978-003
Aeroelastic Studies D159-978-004
Preliminary Flutter Analysis D159-984-001
- The "model numbers" (Model 103, Model 105) referenced relate to different design permutations. IMHO, it appears that the "model numbers" are subordinate to the Bell D-number. (In other words, if this was Boeing, the report might refer to the "D159-105" instead of "Model 105"). Note that the model numbers are explicitly used in the report's body text (example follows)
"A reconnaissance aircraft weapons system capable of achieving range and altitude performance not possible with any current prototype or production aircraft has been designed for operational use in 1956. This aircraft, designated Model 105, is designed specifically for very-high-altitude operation at high sub-sonic speeds using presently available turbojet engines and conventional air-frame design and fabrication practice. A three-view of Model 105 is shown in Figure 1, while Figure 2 presents a cutaway profile showing the cockpit and pilot provisions, landing gear installation, aircraft equipment, airframe structural design, and provisions for the photographic reconnaissance equipment specified in Exhibit A of USAF Contract No. 33(616)-2160."
- The redaction of the camera equipment information is perhaps less puzzling if you note that the original declassification date of the document (from Secret, to Confidential, to Unclassified) was 31 December 1965. It's likely that the camera gear was in use at that time on the U-2 and therefore still sensitive. The original markups were probably replaced by blackouts when the PDF was generated in response to the FOIA request.
HTH!