The L43 was rather weak as a 4 speed; it's also got a side shift, which none of the rest of the trannys have. The L52 was modded by Marlincrawler as an L54; I believe the gear ratios are on his site.

No cons really; the 22R wasn't that much bigger. In fact, the Japanese 21R-U was a bolt-on to the L52, so I think you'll be okay with the G or W series. An R series would be more desireable if you want to upgrade to a 22R or even a 2.7L later on.

You still haven't mentioned what you're putting this into, other than a 4x4. If it's past an 83, you'll have some crossmember work to do with the L-tranny, if dropped in all together.