I have written the reply below to the best of my knowledge and will edit as necessary (so if I have information wrong please PM me and I'll edit this post) as can only go with what I have seen on the conversions, I may not an automotive engineer but friends of mine are so they have offered me some views on what is out there as we have discussed what to do with the steering on my bus; ultimately I want power steering and a rack on my bus, no particular reason, more that I can do it so will do it
There are a number of ways to convert the steering on the busses, some are off the shelf kits, others home brew.
Of the commercial kits I have seen I have noted the following:
The Midland Early Bay (MEB) & Creative Engineering (CE) new 'Danbury' bay both retain the original VW tie rods and substitute the drag link and steering box for different parts. I am sure the CE kit also uses the original VW pitman arm but not sure on the MEB kit, it either uses a modified/new arm or the stock vw item; either way they are retaining alot of the VW kit and subbing out the box.
On either kit is looks like you remove 1 vw flexi coupler, 1 vw steering box and a vw drag link (2 joints) and sub in parts from either kit above
The Midland Early Bay (MEB) kit is nice and simple and £950. I would guess you replace the VW parts noted above with 1 UJ, 1 rack and the equivalent of 1/2 a drag link (so 1 joint to the pitman arm)
http://midlandearlybay.com/Steering_Racks.html" onclick="window.open(this.href);return false;
Creative engineering do not appear to make a kit for old 'bays' but do a replacment for the new 'Danbury' bays, not sure on price but £850 is what they ask for the splitty ones
If the 'Danbury' bay set up is a varient of the splitty one when remove the VW parts and add back 2 UJ's, a rack, a transfer box and 1 joint to connect to the pitman arm (so similar to the MEB one but a couple more components in the uj and transfer box)
http://www.creative-engineering.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=51&category_id=47&option=com_virtuemart&Itemid=26" onclick="window.open(this.href);return false;
http://www.creative-engineering.com/components/com_virtuemart/shop_image/product/LHD_496f17cca42f7.jpg" onclick="window.open(this.href);return false;
http://www.creative-engineering.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=290&category_id=162&option=com_virtuemart&Itemid=26" onclick="window.open(this.href);return false;
The conversion done by Rupert on his spit is cheap and simple and a little like what you get from MEB but homebrew and using a modified or replacement pitman arm.
Note that these kits all use the original bay track rods so the steering does what it was designed to albiet with the 'turning' part done by rack and not steering box.
Other than that there is always the R9D suspension AND steering rack, this is a totally different set up to trailing arm and uses wishbones and a rack, pretty sure parts are off a T25 and guess what, a T25 uses wishbones and rack.
I did see the prototype CE airbag and centrally mounted rack kit at VOWO at the weekend, I have 1 question. Bumpsteer?
The lite steer conversion is interesting, will have to offer up an early and late steering box and see what they intend to do, I imagine is is reducing the ribs.
Now, considering the above I will still be fitting a Rascal rack this summer but in a different format to Rupert, more along the lines of the CE kit (insofar as a couple of UJ's, a transfer box and a rack). I have all the pieces there ready to go, but for the last couple of years I have been too busy on other projects (and still am hence this summer, fingers crossed)