Advice on condition of power steering rams

[Gedfish]

Hi there. I have a Ford 4110 diesel 2WD, 1988 model. The hydraulic steering rams are leaking. I've examined the pistons on the rams & I notice they have some chips and pitting on them. I figure that if I just put in new seals then the rough patched on the pistons will quickly wear the seals & the leaks will start again. So, how bad do the silver pistons have to be before it's not worth just fitting new seals? Are a few nicks & scratches OK? What are new after market rams like?? I understand that you have to replace the whole assembly. Thanks, Ged