Akanexpress, my replies in blue below:

Sometimes we have a good reasons to change manufacturers components in our vehicles.
It may be the case that we still have a used car with solid chassis but we require an easy to maintain or reliable engine or  at other times we may have Vehicles that parts are not readily available in the market for easy replacement/maintenance.
We know that  our local technicians  can fix say Nissan engine in a Toyota or Volvo. At times, cosmetic surgery are done to fix say Audi head/back lights to Opel or Mazda, and vice versa.

Pls Nigerians apart from the above what else can be changed in a vehicle apart from the engine? Most parts are interchangeable one way or the other except for glass screens / windows.

Can the following parts be locally modified  to adapt from one make of a vehicle to work reliably in another? (say: Toyota to Renault) :-
1.  Shock Absorbers - This depends on the suspension layout and the ability of the mechanic sometimes it is not worth the hassle as many cars belong to manufacturing groups and most of their parts are interchangeblae for example VAG ( Volkswagen / Audi Group ) where most of the floorpans steering racks suspension assemblies are all interchangeable. Another example is Renault and Nissan who share technology as part of the same group, then there is Ford and Mazda and so on interestingly you find these unions with disparate manufacturers such as the latter two, another good example would be in the latest Chrysler 300C for example which was based on the floorpan of the E class circa 1995 - 2003. So one should look for such bedpartners first,
2.  Fuel Injector - If this is a Bosch item they are widely interchangeable - again this will depend on the loom and the threads on the inlet manifold
3. Wiring to Dashboard - Speedometer/Odometer (That is can a BMW 520 with Totota Cressida engine  be wired to read the Speedometer, Odometer, etc) -

[/color]Possibly ,  worst case you can use the Toyota clocks in the BM dash[color=#000099]

Pls contribute yr idea, experiences, recommendations and limitations