Ahhhhhh Gear talk!..... Seems like yesturday I was in the same spot, and got it wrong.

Now, take into account, that BB had a supercharger. So my experience is with a very light tire, (km2) Light wheel (Weld Racing at the time, PMtruck Wheels now)

So if your truck is a slug now with the toyos, and whatever wheels you have, You may want to consider 4.88. If its "livable" with 3.73, then I say go to 4.56.

What you are giving up with the 4.88 is the highway criusing gear. BB was SLOOOOOOOOW with 4.88s. I swore I ruined her. with 4.56s now, she is still not the rocket she was with 4.10 on the highway. But she is more responsive across the RPM band.

Gears are a leap. You want to be certain you get it right the first time. The expense for doing it twice is horrendus.