I busted my front 5.29s in my 4Runner and I am running some leftover 3.90 thirds from an '81 welded up to get through snow wheeling season untill I can afford some good new parts. I have 4.7 in the t-case so wheeling is no problem.  I run a 3RZ, which to my suprise has enough extra snort that the 3.90s are actually tolerable for the day to day driving and I can still pull 75 on the highway no problem even with 35" tires.  No don't get me wrong, headwinds suck and I can't use 5th gear at all but it's way better than stock gears with a 22re.

I have a buddy with several 4.56 V6 thirds that would be very very cheap.  I am thinking of trying them out instead of buying new 5.29s since they are rediculously available and easy to obtain if I break.

So my question is this:  Is anyone running 4.56 with 35s or 37s and a hot 150hp 4 banger?  Is it still like "Oh this sucks to have stock gearing!" or is it within the acceptable range of drivability still using 5th gear sometimes etc?

This seems like a dumb question but all I've ever ran was 4.10s and 5.29s so I don't have any idea what the ratios in between feel like.

It'll be better than 3.90/4.10s, but not as peppy as the 5.29s. Lol, if they're cheap enough, and worth it to you, just get them and run 'em til you can get the 5.29s back.  You may decide you like them for the highway running aspect.  Save a little fuel, save a little earth, right? 

I travel a lot in my truck, so I'm sticking to the 3rz and 4.10s and 33s.  When I get new tires and wheels, I will be doing 4.88s and 35s. 

How cheap we talking?    I say get them if they are a good deal.  They are better than 4.10s for sure i can tell a difference between 4.10s and 4.56s.

That was always my go to spare diff a 4.56.  And everybody knows i have blown up enough 5.29s and had to run a 4.56 or 4.10 to drive to work/school until i could get another 5.29 installed.
With that said 4.56s were not too bad with 37" toyos in a second gen runner with a 3.4L. Im guessing with 35s
In a pickup with a 3rz would be even better.

I use 5th all the time.  Only down to 4th or 3rd if I really wanna maintain 75-80mph up a decent hill, or pass someone quickly.  At 75mph I'm doing about 3k-ish RPMs.  Maybe a little higher, I can't remember.  But you know the 3rz loves to run.  Mine loves running through the revs...  And i get about 17mpg.  Whether I'm running 60 or 80.  I did manage to draft a semi a bit one night and got 21.5mpg.

I'd go with the 4.56's.  And then save up for some 5.29's.  Especially, if you can get them as cheap as your saying.  And you can keep them for spares later on if need be.  Or sell them for more.