Basic to Advanced and back?

[loksvassago]

I'm going to give a short preface here: I don't really post on this forum much (if at all, going by my post count...), but I had a burning question that you guys seem in a great place to answer.

Specifically, although my first exposure to D&D was a Red Box, I never REALLY was exposed to D&D until 3rd (3.5) edition, and I never really PLAYED until 4th. Needless to say, there is a bit of a gaping hole in my D&D repertoire.

This has led me to wanting to run a very simple "old school dungeon crawl" using one of the "old school" simulacrums. This is where my question comes in -

Specifically, what are the important things I would need to account for if I wanted to run a module designed for use with b/x in AD&D instead? As I understand it AC might need a minor adjustment (as one began at 10 for unarmored while the other began at 9), but is there anything else I should know? I know I could spend many hours reading OSRIC and Labyrinth Lord backwards and forwards until I spotted the differences in all of the THAC0 tables and whatever, but does anyone have anything that comes immediately to mind in a big way?

If this isn't quite the right forum for this (it's SORT OF about basic/expert and advanced D&D, given I'm using two simulacrum rulesets) sorry.

 

[ExploderWizard]

The biggest differences will be in the PCs themselves. There are more classes to choose from in advanced. Ability score adjustments are very different too. A basic D&D fighter with an 18 strength has a +3 to hit, damage, and open doors. An advanced fighter could possibly have an 18/00 strength and end up with +3 to hit and +6 damage. If weapon specialization is used it could be +4/+8 with 3 attacks every two rounds.

Other differences include the basic 1st level cleric gaining no spell abillity vs the advanced cleric starting out with multiple spells (with WIS bonus).

Magic users and thieves are fairly close to each other at the lower levels although thieves abilities in the advanced game will be a bit higher.

Equipment wise, basic characters start out much better off than their advanced counterparts. A basic fighter can easily affort plate armor while an advance one will probably start with scale or chain (or splint/banded with a lucky roll). This means basic characters will have better ACs starting out on average.

Monsters will require very little to no adjustment at all.

As far as general rules and gameplay goes, advanced just has more bits to keep track of such as the segment oriented initiative system.

I have run Keep on the Borderlands with AD&D and didn't need to do any conversion work at all. Good luck. Be sure to give us a play report of how it turned out.

 

[Viking Bastard]

This seems pretty comprehensive:
D&D to AD&D Conversion Notes

 

[loksvassago]

Wow, pretty fast replies! Thank you both, this has been a huge help - I was hoping to give my prospective players the choice of b/x (Labyrinth Lord) or AD&D (OSRIC) with a brief explanation of the differences, then done most of the necessary converting work on the monsters depending on how they stacked up against the PCs of either edition. It looks like I'll probably need to (potentially) change their saves and maybe add a +1 here or there (it's a low level adventure) if they choose OSRIC instead of LL but otherwise nothing too challenging - I'll be sure to remark on how well I managed when I get around to running it