All sounds like alot of work.

Just get a good used diff and plug it in the rear and go.

Here's a few V6 4.10 geared diffs I found.
IF you have 4.10 gears anyway.

Quote
1989
Carrier
Toyota Truck C F01182 $125 Eckert & Sons Auto Parts USA-TX(Stonewall) E-mail 1-800-950-8014
1989
Carrier
Toyota Pickup/Stout 6/89,3.0L,5SP,BASE K166 $75 Cousineau Recycling USA-WI(Antigo) E-mail 1-866-330-3730

85 4Runner - With NEW Marlin 4.7 Gears!! It's a whole new beast!