This 1978 Civic is on ebay at the moment for £3000 buy it now.
At that age it will be tax, MOT and ULEZ exempt. The reg is RJY 893T shown in another photo.
https://www.ebay.co.uk/itm/364126335003
by far the cheapest headgasket to use is the d16z6 headgasket as it's the most common, basically all gaskets for SOHC d series of the 90-01 era are interchangeable.