As always, depends. There was a early grey market for RRC's. Those would have been dual carburetor 3.5l petrols up to 1985. EFI introduced in 1986 for the 1987 re-entry into US market. There are also late 70's and mid-80's RRC's available every so often and they have a variety of engines.
Head gaskets on early Land Rovers was not an issue. My son has a 89 with over 250K and original head gasket. My 98 Disco has a new head gasket only because the front cover sprung a small leak and since I was pulling the front end off it was convenient to upgrade the cam/lifters from D&D. I also have a 95 RRC LWB with a cam'd 4.6 that has over 100K miles on the swap. Properly maintained a 3.5/3.9/4.2/4.6 can go over 200K miles on head gaskets. The issue is the dumb owner who neglects maintenance, doesn't change hoses, blows same or lets a small leak deplete the coolant level such that air gets in the system and it overheats. There is also discussion of tooling wearing out at the end of the production run for the old Buick V8, in the year 2001+ timeframe. That is probably an issue but the bigger problem was the owners who neglected to stay on top of maintenance and aging issues.