When you say the instruments don't work what exactly do you mean? The temp' gauge works with an ether filled tube, not electric.It is one continuous unit from sensor at rear of cylinder head to gauge.The fuel gauge is electric. If that doesn't work it's usually a bad earth/ground. For your belt and braces you should be able to source a "t" piece which should screw into the head. Don't think that a capillary tube for mechanical gauge would be vert reliable fitted into top rad hose as in my electric rad' fan, it would fluctuate with the opening and closing of 'stat. Specialist workshops are able to sort out the ether tube gauge, but what do I know
