Glad to see you've come out of hibernation Chris
Here's the tube I inserted into the lower holes in the rear uprights (you need 80mm per side if memory serves me correctly):
STEEL PRECISION TUBE 14mm OD x 300mm LONG 1mm WALL
And these are the bushes I stuck in the top of the uprights (£22.70 for a pair):
Mazda MX-5 Rear Upper Inner & Outer Suspension Bush SPORT poly STRONGFLEX
My column to rack UJ is rally design part#
RD820F
Hope that helps!