I am talking to Vansteel in the US
IT may be easier to buy a set of their double offset arms
which move the spring mounting point inboard and inch each side
and does away with the problem of the Tyre to spring clearance issue
although it requires a modified spring.
Has anyone tried this conversion
Bfit
What size rim and tyre you plan on using?
I am using a 1/2" shorter per side spring with standard trailing arms. The rims are 18 x 9.5 with a 5.25" backspace. The picture shows about 3/8" clearence between the spring and rim.
If I used a 5.5" backspaced rim then I would have gone for the double offsets.
Another problem you may have with 5.5" backspacing is the tyre rubbing on the front of the frame kickup area. The frame is wider here then at the top of the tyre.
[IMG=700x525]http://i1233.photobucket.com/albums/ff391/wabco40/IMG_3798.jpg[/IMG]