How do Rum and Lucky Duke/Horse Shoes interact?
Another possibility:
This doesn't follow the letter of the rules, but since it's a translation, I think it might be more appropriate to attempt to follow the spirit of the rules.
There's several characters (most, even) whose special abilities essentially are like having a &quot;built-in&quot; item. Willy the Kid has a built-in Volcanic, Paul Regret has a built-in Mustang. I think the intention for Lucky Duke is to have built-in Horse Shoes. Although the wording is different on Lucky Duke and Horse Shoes, for any standard single-card &quot;Draw&quot;, the effect of either one is the same.
Continuing with this logic, the correct way for Lucky Duke to use Rum, would be to draw an extra card, for 5 total. And if he has Horse Shoes, then he gets one more for 6. This is much like Jourdonnais, who has a built-in barrel. (Okay, Jourdonnais' ability isn't exactly a barrel since it only applies to Bang! cards, but it's darn close.)
This isn't official, but in addition to the reasons above, I think it makes sense from a balance perspective. Lucky Duke definitely shouldn't have a disadvantage for a luck-based card like Rum, but drawing 8 cards is perhaps too good. See the probability discussion below, and you can decide for yourself how good Lucky Duke's ability should be.
Probability simulations:
From our comments, I got curious about how much of an advantaged each of these methods would allow. I coded it up and a million simulations of each. As I suspected, the drawing two-at-time method is nicest (but it's not as much of an improvement over drawing 5 and choosing 4 as I would have thought). The means (and standard deviations) are in the table below, and the graph below that shows the distribution of unique suits obtained under each rule. If anyone wants to see the code, leave a comment and I'll edit it into my answer.
Draw 4   Draw5   Draw 8
   2.7     3.1      3.3
  (0.63)  (0.64)   (0.56)


Under the draw 5 rule and the draw 8 rule you're the odds of gaining 3 life are about the same (58.8% and 59.9%, respectively), but you see an increased chance of only gaining 2 life in the Draw5 rule.
  Gain    Draw 4   Draw5   Draw 8
2 life    30%      15%      6%
3 life    58%      59%     60%
4 life    11%      26%     34%

I abbreviated the draw-2-at-a-time rule to &quot;draw 8&quot;, but I modeled it appropriately as two-at-a-time, picking one of the first 2 randomly, then for each subsequent two cards picking randomly unless one suit was already selected and the other wasn't. Each set of draws was from a 52-card deck with 13 of each suit. I'm not sure exactly how many cards Bang uses, but it's probably close enough.