Oxygen hatch relocated to below starboard wing, fuel and MW-50 fillers moved one frame forward to frame 2, frame 9 redesigned, radio hatch moved to frame 4 and set slightly higher, hand and footholds deleted in frames 1 and 2 starboard, main compass hatch deleted from frame 2 port, D/F loop moved to frame 3 (not reproduced on the model for obvious reasons), adjustable trim tabs on ailerons and rudder, increased use of steel and wood to replace strategic materials (notably the tail assembly), theoretically retracting tail-wheel (not systematically fitted), fully-covered wheel wells (covers often removed or not fitted), systematic use of final type of wheels necessitating the "rectangular" wing bulges, etc, etc. Shall I continue? As far as possible given the fact that we don't have access to the GMAX source, these have been reproduced on our version. It is the most accurate K-4 available for CFS3, both visually and aeronautically.
The K-type was a new model and so benefitted from a greater degree of standardisation than the G-10 which was produced concurrently. Contrary to popular misconception, by the way, the K-4 was NOT the successor to the G-10! Both models were produced simultaneously, with the G-10 entering service actually a week or two after the K-4 if I remember rightly. The G-10 was what the bikers would call a "bitza," designed to use G-type parts as far as possible to produce a similar aircraft to the K-type. As a result, there were wide variations among the late G-types (many of them internal), while Ks tended to be essentially standardised in comparison.