Which wheel cylinders?

Hi folks,
Could anyone tell me how to tell the difference between brake wheel cylinders? I have a bitsa that has not been on the road for a few years and was going to swap the wheel cylinders as a precaution but which ones do I order? The fronts have 1 1/2 inch moulded into them if this helps but I cannot see any other markings on them. As an alternative could I just replace the seals? Is that much of a job? Would I still need to know whether the fitted are metric or imperial?
Cheers.
Malc.

Put a picture up of them.

Give us a clue what axles you've got fitted.
Seals are worthwhile ONLY if the insides of the cylinders are in very good condition - brake fluid absorbs water & can lead to pitting inside which is just one reason for regular changes. I once assisted with a post RTC vehicle exam where brake failure was claimed - my crewmate was an authorised examiner - & what came out of the system was badly water contaminated.
For rare cylinders in poor condition it is possible to have them bored out & lined but I doubt LR ones have got to that stage yet.