Red Tail, I saw that P51-C in your picture last weekend here in Omaha. Great airshow with plenty of WWII birds.
Anyway, on to your query...
North American had two factories producing P51s. One was in Inglewood, CA, the other in Dallas, TX. The only difference between the B and C models is where it was produced. Those produced in Dallas got the C designation and those from Inglewood got the B. Other than the designation, they were identical planes.
The early B&C models were powered by the Packard-Merlin V-1650-3. It is a 1649 cubic inch engine producing a maximum of 1620 horsepower on WEP. The later models were powered by the V-1650-7 (the same engine in the P51D). It too is a 1649 cubic inch engine but produces a maximum of 1720 horsepower on wep. The difference between the two engines is the two-staged supercharger on the 1650-7. That was what gave it the added horses.
Some other subtle differences between the early and late models are in fuel capacity, weight and service ceiling. All were outfitted with 4x.50 caliber wing-mounted machine guns holding 350 rounds each in the outer pair and 280 each in the inner. All could carry armaments of 2x1000 pound bombs on hardened wingpoints, not the 500 pound max that is modelled in AH.
Well, I believe that about covers the P51 for you.

BTW, there will be a quiz.