Late IIa servo unit query

Can anybody sugest a good fix for a late IIa servo unit , at present I am using one on a hybrid 68 109 diesel 2.5 n/a on a strenched 1986 range rover chassis. I was wondering if was possible to change the pedal bar from a early defender. The servo I am using at present (and just packed up) was off a late 1960's early 70's IIa 6 cylinder, with the large round plastic reservoir intergrated into the master cylinder. single circuit brake system.
Many thanks