Much has been published with reference to the identity of many different Ferrari models. Some span several volumes and deal with each chassis number separately. Clearly, detail like this is outside the scope of any small volume and the value of many of those important cars warrants detailed research.
Excerpt from ‘Sports Car Pocket Guide’ by Michael Duffy
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While the earlier XK’s were fitted with separate chassis, the new Jaguar E-Type was a sheet steel monocoque in the mold of the D Type race model. The E types were initially available in only two configurations: coupe and roadster, both two seaters. Over time this model would evolve; the 3.8 engine was replaced with a 4.2 liter unit in 1964 and at the same time the gearbox was updated to a full syncromesh unit. Covered headlamps and triple carbs were missing from the 1968 Series Two model; now with open headlamps and twin Strombergs. 
The new, Pagoda Roof SL’s began with the 230SL. All of the later six cylinder SL’s, the 230, 250 and 280 are very similar in appearance. Under the skin, there were a few differences. The 230SL like all of the Pagoda Roof cars, was fitted with a fuel injected 6 cylinder engine. These early engines carried a four main bearing crankshaft and were fitted with disc brakes on the front only. Later on the 250 and 280 models, four wheel discs were standard as was a new, smoother running, seven main bearing engine. These later cars are commonly found fully equipped with automatic transmissions, power steering and air conditioning.
The 1953 and 1954 Covettes featured a six cylinder engine and GM’s Powerglide,
two-speed automatic; the first big change for the Vette arrived in 1955 with the optional 265CID, V-8 engine. The 235CID Six was dropped in 1956 as were the wire mesh
headlamp covers. The V-8 was offered with HP options as high as 240 but the
transmission choices remained the Powerglide or the three-speed manual. Things
started to get interesting in 1957 with engines (now a 283CID) offered with
optional fuel injection with ratings as high as 283HP. A four-speed transmission was finally offered as an option late that year. For 1958 the three speed was dropped and the Fuelie could be ordered with ratings as high as 290HP. Engine
specs remained basically unchanged for 1959, the bodywork was updated at the front with distinctive twin headlights (which would stay with the car through 1962).Excerpt copied with permission from ‘Sports Car Pocket Guide’ by Michael Duffy. For more info or to purchase, go to….. http://www.amazon.com/shops/hc-books
Ferdinand Porsche’s early efforts relied heavily on the parts bins at VW for engine cases, gearboxes and steering. As time went on, more and more of those parts would become unique to the Porsche. Early, VW based 1100cc engines would give way to Porsche’s own engines (and the two piece Split Windshield would be replaced by a Bent Screen) in 1952. At Max Hoffman’s prodding, the Speedster appeared in 1954. These early 356’s are generally called, pre-A’s: early cars with 16”wheels, minimal bumpers and sometimes fitted with roller bearing crankshafts (though these cranks were available on early A models as well). This changed in 1955-56 with the 356A. The V windshield was replaced by the curved screen, 15” wheels replaced the 16” version and over the life of the A, the VW steering box would be replaced with a ZF unit, wheel bearings and transmissions were updated and in 1957, the bee hive tail lamps would be replaced with the teardrop type that would appear on all 356’s until the end of production. Excerpt copied with permission from ‘Sports Car Pocket Guide’ by Michael Duffy. For more info or to purchase, go to….. http://www.amazon.com/shops/hc-books
XK Jaguars were offered in Fixed Head coupe, Drop Head convertible/cabriolet and roadster versions. The Fixed Heads FHC and Dropheads DHC models featured wood facias/dashboards and broadcloth headliners in addition to the leather seating and Wilton wool carpeting that we now associate with these quintessential British sports cars. Excerpt copied with permission from ‘Sports Car Pocket Guide’ by Michael Duffy. For more info or to purchase, go to….. http://www.amazon.com/shops/hc-books