In the Gabor line, there are two colors that are going to be similar to Henry Margu's 8/14H:
GL8/10: Dark Chestnut and GL10/14: Walnut
GL8/10: Dark Chestnut is going to be the closest in terms of base colors because it has the same base shade (#8) as 8/14H, but it is going to be darker than 8/14H since it has a warmer blend of medium golden brown and caramel brown.
Heather's review showcasing GL8/10: Dark Chestnut: https://www.youtube.com/watch?v=spUY2yx38Xo.
GL10/14: Walnut is going to have the same blended ash shade, but it is lighter than 8/14H due to the blend of honey blonde in it.
Between these two colors, GL8/10: Walnut looks to be the closest to 8/14H since it is a dark color and has the same base shade.