PCM For 1991 W250 with 5.2l, 4wd and manual transmission

I'm looking for a good, in working condition, PCM for my dad's 1991 W250. I'm hearing it has to be specific for a manual transmissionand 4wd vehicle? I can't confirm if that's true or not and we are researching that now. I'll post part numbers if there's markings on PA. He's having a charging issue and the mechanic is saying it's the PCM?

Thanks, Carl
Sellersville, Pa.