Handling rules changes from Season 0 to now

[Jiggy]

I'm running a Season 0 scenario tomorrow, and in prepping it, I've come up with a question that I'm not sure how to answer:

What do you do when you spot something that's written around a rule working in a way that it no longer does?

Examples:
If there's a cleric with heavy armor who hasn't spent a feat on proficiency (since they were auto-proficient in 3.5), do I treat them as proficient or nonproficient?

Poisons: in 3.5 it says (according to what I found in the SRD) that even if you make the first save, you might still take the secondary damage. But in Pathfinder, making the initial save means you're not afflicted, no matter what. On this one I'm pretty sure I should run it "the new way", but I thought I'd include it just in case.

There was another example that I can't remember, so I guess that's it.

Thanks!

[Michael Brock]

Leave the cleric as is and just roll with it.

Run poison the new way.

This is one reason I'm considering updating 7-8 of the classic, need to stay around scenarios and retiring the rest. Still up in the air and very, very infant stages of this idea so please don't get worked up over it. I will poll the playerbase before we did anything like this.

[Jiggy]

Wow, guidance from Lord Goldhelm himself! Thanks!

[Michael Brock]

You are welcome. Things that can be easily converted, like the poison rules, should be converted. Things that are more difficult, like rebuilding the entire cleric, should just be used as written.

[kinevon]

Jiggy, you could always just treat it as a non-optimal Cleric archetype that gives up Channel Energy for Heavy Armor Proficiency. ;)

Mike, does that helm protect against Blindheims?