The chassis number is the main identifier of your vehicle. It is stamped on the right hand wing valence of the engine bay bracing bracket. It is also stamped on the Commission or Compliance plate, which is found on the engine bay wall. The prefix to the chassis number will be the number 2 followed by a letter, ie: 2J for Jaguar 4.2 models  - 2G for Jaguar 5.3 models   - 2H for Daimler 4.2 models   - 2F for Daimler 5.3 models.  The chassis number then follows these prefixes. Right Hand Drive vehicles [RHD] have four numbers starting from 1001 and Left Hand Drive vehicles [LHD] have five numbers starting from 50001. All the chassis numbers are then followed by a suffix of BW.   Confused ?

For example, I own a 1976 Right Hand Drive Jaguar XJC with a 4.2 litre engine. So my chassis number is 2J2291BW.

Jerry Liudahl lives in Eugene, Oregon USA and drives around town in his Left Hand Drive 1976 Jaguar XJ6C. His chassis number is 2J51730BW.

Your engine number is stamped on the top of the cylinder block, at the rear of the engine. It will also be stamped on your Compliance or Commission plate, which is found on the engine bay sidewall. Engine numbers for the XJC continued from the same range used for the series one models.

                   4.2 litre engines 7L.74000 (approx)  to  7L.99999
                               then      8L.1001 onwards
                                           these numbers then finished with a single letter ie: L or S  

                   5.3 litre engines 7P_ _ _ _ _ then finished with 2 letters such as SA, SB,  LA

If there was a sequence for this numbering system, it was impossible to follow !  
Example:  

the first V12  coupe imported into Australia was chassis # 2G1113  Engine number is 7P26269 SB.  
The 2nd V12 coupe imported into Australia was chassis # 2G1115  Engine number is 7P26303 SB 

Manual gearbox: your gearbox number will be found stamped on the left hand rear corner of the gearbox casing. It will also be stamped on your Compliance or Commission plate, which is found on the engine bay sidewall.

Auto gearbox: your gearbox number will be found on a label affixed to the left hand side of the gearbox casing. It will also be stamped on your Compliance or Commission plate, which is found on the engine bay sidewall.

Your body number is stamped Compliance or Commission plate, which is found on the engine bay sidewall.  The body numbers are somewhat similar to the chassis numbers in that they use the letters F, G, H and J with 5 digit number combinations.  The difference with body numbers is that they begin with the number 5 and not 2.  Example: chassis # 2J2462 is body # 5J5430.

Again the numbers do not always run in the proper sequence as in this example from some of the original 4.2 coupes delivered to Australia.  

               chassis # 2J1582  despatched on the 22 Oct 1975 has the body # 5J2586

               chassis # 2J1588 despatched on the 04 Nov 1975 has the body # 5J2579

Maybe the body went missing on the line somewhere, then when they found it again, chassis 1588 was going by !  I suppose there must be a reason why this sort of anomaly is found, just cannot think why ?