I dont want to be a fuss-pot, but.........
I cant take the credit for this info, as i sourced it of the net
The line didn't get much of a change until after Princes merger with Nissan. From July to September of '68, the New C series Skylines were introduced. The first was the New C10 1.5 liter G15 powered 1500 Sedan, with the Skyline 2000GT(GC10) G18 1815cc engine following.
1969 Skyline 2000 GT-R
Then came the first of the Skylines that would form the Skyline Legend, the Skyline 2000 GT-R. Introduced in February 1969, the GT-R(PGC10) benefited from the development of the R380 program. This car was powered by a S20(not to be confused with the later SR20DET) in line DOHC 6 cylinder, 24 valve, twin cam triple 2 barrel side draught monster, developing 160 horsepower at 7000 rpm and racing to a top speed of 200 km/h.
This was followed by an upgraded Standard Skyline, the PC10, a 1.8 liter G18 powered car in August '69, then the Skyline GC10 2000 GT 4 door sedan with a single overhead cam version of the SR20 inline 6 producing 105 to 120 horsepower depending on options. Skyline also had a GT-Xi line of 1500 and 2000 cars before the whole line was once again restyled.
71 GT-X
The fourth series of Skyline began production in September '72 with 5 different versions of the new C110 style. 1.6, 1.8 and 2 liter engines powered the various different model levels.
73 Skyline 2000 GT-r KPGC110
The top level was held by the Skyline 2000 GT-R, the new KPGC110, with the same 160 horse S20 engine of the previous GT-R. This GT-r was actually introduced in January of '73 and is one mean looking Skyline.
1977 210 series 2000GT-E-s
The line continued pretty much unchanged until August 1977, when the 5th series C210 line up took over. The lowest level C110 Skyline had been phased out in October 1975, so the C210 line only had 4 levels instead of the 5.
1980 2000GT-Es
83 2000RS
The line was refreshed once again in August 81 with the new R30 series, a rather boxy boring group of Skylines. It would take several years before the R32, R33, and R34 series
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