Compared to the versions of Liberty City in the late 20th and early 21st century, the 1978 version has many differences. Mainly this is development, mostly buildings being constructed. One major difference is that, the main bridge in the city, the Callahan Bridge, does not exist yet.
Not many changes are in Portland. It is the least different from the other versions. Only three real changes are there. First, one part of Portland Harbor's landfill area is being filled in and is a construction zone at the time. A second change is that the fish factory run by the Triads does not exist either, it is built in around 1980-1985. Also, the freeway that was part of the Callahan Bridge, and the bridge itself, is not yet built. Thus, the roads around where the bridge will later be are noticeably different.
The road map of Staunton Island is the least changed. But in buildings and other features, it is more different than Portland. The tallest building in Liberty City as of 2001 is the Jefferson St. Credit Union Building, which is finished in about 2000-2001. In 1978 the tallest building in the city is an unnamed building loosely based off the Empire State Building.
Like in Grand Theft Auto: Liberty City Stories, the buildings in Fort Staunton still exist, prior to the explosion that destroyed the buildings. The last difference in GTA: LCP's Liberty City version is a slightly different road map where the Callahan Bridge would connect Portland to Staunton Island.
Shoreside Vale has some very noticable changes. In Cedar Grove, two mansions including the Cartel Mansion in Cedar Grove do not exist. They are replaced with a steep road that goes between their future sites. In Pike Creek, a small industrial neighborhood, two blocks of the area do not exist. Instead it is a grassy field. At Francis International Airport, one runway is not yet built. Considering that the runway was landfill anyway, it is filled in most likely because of expansion of the airport. In Wichita Gardens, two of the apartment projects are not yet built. They are instead replaced by a playground and a park. Finally, the tunnel connecting Liberty City to Upstate is under construction, but only slightly. Just about 50 feet of rock on each side has been blasted, with a sign saying "WORKER STRIKE - BLASTING DELAYED UNTIL FURTHER NOTICE". This makes sense as there were many worker strikes around the country in the 1970's.