vauxhall,
If you are looking for a diesel conversion head the RJL head is the way to go. Now if you are looking to get away from the Cox glow head and are wanting to use glow plugs then the only way to go there is the Galbreath head and Nelson plugs from Larry Driskill at
www.kittingittogether.com any other glow plug conversion will loose power in a Cox engine with the Galbreath/Nelson set up you will gain power.
Later,
Tim