Not aware of a supplier of rebuilt boxes or aftermarket boxes in the UK....
rebuild well in theory any mechanic or reasonably competent enthusiast should be able to but they do look quite complicated....a manual box is way easier
if you can establish the version of the box and navigate Rockauto site you can get a bearings seal and shim kit for notta lotta cash for a rebuild no problem
Edlemann 8539 looks about right
https://www.plews-edelmann.com/repair-kits/
The box is a chrysler built copy of a saginaw design anyone who can rebuild a box for a chevy or ford can rebuild this box.
but given them a copy of the factory service manual when they do.
here
http://www.mymopar.com/index.php?pid=109
same site has parts books as well...get one of them while you are there
http://www.mymopar.com/index.php?pid=107
if the ware is in the teeth of the sector or the worm screw better parts will be necessary
the rest is not going to suffer that kind of ware
worm screw bearing surfaces can pit but a competent machine shop and cut and sleeve.
Option 2
if you want a new one bergman autocraft sell a borgeson designed Delphi (saginaw) made box that was designed for a modern vehicle but has the appropriate mountings for an old mopar
bergman provide a kit of parts to allow it to bolt right in to you car with the original pipes and pump and steering column
Option 3
US rebuild from reputable company
steer and gear
firm feel
borgeson
all do nice rebuilt boxes
you buy your rebuilt box from them and send yours or find one on US Ebay to send to them as a core (reduced postage) to get some money back
option 4 take pot luck with a rebuild from rockauto Nappa or any of the other generic US parts suppliers some of which hawk their wares on Ebay
slop in the centre of the box is either worn bearings or bad adjustment allowing both worm screw and sector to slap about or jump up and down
or the teeth on the sector have worn a tooth like shape into the ballnut teeth. one or both could be scrap.... both are robust pieces so unless there has been serious neglect or the box has received attention from a geezer with a file who made a mess. i'd suggest they will probably be ok.
more cars had power steering than manual so New Old stock parts appear on ebay from time to time.
if stuck i think rodley motors used to have a rack full of second hand boxes...you won't know what you have got until its fitted or dismantled but could be a supply of parts....
initially Id check it wasn't play at the slip joint in the steerings shaft coupling
if not
Id then then try adjusting the sector so its a bit stiff turning the steering wheel, make it slightly stiff in the middle with the wheels off the ground. this is done with a stud and lock nut on the top of the box when its in the car
then you could try to pri out the lower seal and replace with new but seat it a 1/4 - 1/2 a mm higher into the case
see how ya go
if you take the box out
try to avoid moving or loosening the manifold that the pipes go into. its position on the case dictates the level of assist-balance between turning left and right
get it in the wrong place and the steering wheel will spin with vigour to 1 lock or the other of its own accord, and finding the sweet spot again to stop it doing it can be hard work. there is a jiggly little pin under there and its position in the middle of its jiggle is vital to normal operation
Option 5
Manual steering
need an adaptor/extender for the steering shaft spline and potentially a new pitman arm but not necessarily depends on year
id suggest 20:1 for a B body and 16:1 for an A body
your power box is 14.5:1 ratio
Dave
