Edit/update August 4 2015; This is a real project now. f you want to skip to the actual project/solution, skip to Post #10. I am picking things up there and will document the work as it happens.
Previously edited this entire thread. I started it before getting into the idea of building a set of lifted front struts and coil over springs, but that looks like where this going. This is pretty long winded so I'll breakit up into sections
The goal: 2” front lift and ability to use 29”-ish tires. Preferred size 235 75r15 just because they are super common in LT.
Transmission gearing and diff ratios are already accounted for. If I swap the diffs back to 4.3 it will give me essentially the same engine RPM to ground end ratio that I have now, with extra ground clearance. I realize I will need to trim wheel wells, Can possibly get away with just trimming the plastic that wraps from side trim panels, but we'll see.
Already tried:
-I did the 2” lift using Tim's method of building lift blocks for the top mounts. But, it doesn't raise the spring perch, so I can't run larger tires. In actual use I have caught oil pan, transfer case, exhaust and diff mounts when on dirt roads and really could use that extra clearance. If I am taking it apart again, rather than just replacing tired front springs, may as well really do it up.
- I tried to find other struts that would take care of it. I referenced Zenseeker's suspension page with possible strut replacements, and referenced to Monroe's dimension chart. I looked at mount type and stock tire size on the other models of cars. The one that came out the winner dimensionally was the model for Ford Escape/ Mercury mariner/Mazda Tribute, with the model for Hyundai Sante Fe runner up. So I went to the pick n pull and found these. Neither had bottom mounts that would bolt to the previa steering knuckle. I consider the one for the sante fe as completely incompatible. It is for a 1” thick steering knuckle and the Previa's is 1 7/16” The one for the Ford/Merc/Mazda is kind of closer, it is 1 7/16”, proper thickness, but hole spacing and holes themselves are smaller, and there is not enough metal in that part of the strut to mod without welding on extra metal and completely re drilling. May as well weld extensions on the bottom of stock Previa struts, but I don't think anyone around here will do any welding on a charged strut.
I also had a quick look at an earlier model Sienna strut and the spring perch was not high enough, so I didn't even take other measurements on it.
I still want to see the strut for the Mazda MPV before launching into a coil over project, but I have my doubts.