With the pwr ur pushing and from what I've read how u drive, there is another option that requires work but nothing u couldn't handle.... but not sure if u'd want to go down this rabbit hole as it sounds to me ur looking for a quick turn around. The strongest version on the A340 made comes with extra friction disc, billeted internals, larger TC, larger front pump and a # of other upgrades... and there are after market parts u can run to help with better shifting (the ones available to for any A340).
In order to run the larger TC would require a custom spacer and a few other things or u can run an OEM sized which would save u many fitment issues. The Best part is u can get the trans for around $100-150, people also just scrap them as they want the manual trans, with 30-60 thousand miles on the units. This is a swap I've been planning but haven't had time to do behind a 5vz yet. The JDM Aristo A340E 3f310 came only in 2wd but can be converted to 4wd (I've already done so for my 2jzgte atlas 4 swap 4runner. The case has a predrilled slot for a kick down cable if needed for ur yr 4runner and u can swap the VB to whats in ur trans as all the port holes are the same on the main case (I haven't had time to look into the ability to run a 3f310 VB. Don't have time right now to go into more detail but if this even interests U I can dig up pick of said internals when I partly disassembled one the better understand the unit and difference between the A340 in the 3rd gen 4runner, I also have one seating on a bench so I can get U a pic where the VB bolts up...