Hi guys working on a mates 1967 250s and while checking the brake booster found the oil pressure gauge leaking

have owned a few vintage mercs in the past and never seen this is there a way to fix this or do we need a new gauge? (ps its leaking inside the instrument cluster)
ALSO the speed indicator column cable bottom end (not at the gauge) has come off its got a hook on the end of it found a holder on the column shaft near the steering wheel but it seems to be too loose (tried to tighten (at dash side) no luck

...tested the cable and it moves freely anyone know where the cable should go on the column? or how far down should I have it?? tried about 10 spots can not get it to work per gear changes....any help is very welcome...thanks again...
regards BI