Given the change in tire size (from 27" to 32"), your problem is more gearing than weight - and I know of only one place that offers a lower ratio final drive set, I'll post a link to their website as soon as I locate it.
Swapping in a V6 is possible but you're going to need to swap the engine, transmission, transfercase, ECU, wiring loom and front springs (the V6 is a couple of hundered pounds heavier), so unless you can pickup a donor vehicle with rear end damage, it might be easier to buy a GV and swap your stuff over.
You could also try asking your question over at the ZukiWorld
forum, it seems the folks there are more into modifications than here.
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