Speedometer Cable

if your plastic clip is still good --
I would rotate the square cable a bit & try to slide it in the gauge cluster-- this should not be a difficult operation--- take a flashlight & look at the situation-- not much room-- but the cable should be lined up with the gauge cluster & it is just a mater of getting the square ends to line up--

or remove the speedo cable at the tranny & rotate the inside cable-- to line them up
(you should not need to do this if speedo was working before you started your repair))

or if you want to remove the whole cluster then drop the column& remove the screws & then find the wire harness clips inside the dash & bend them down to release the harness , then pull that harness free from the clips & tilt the gauge assembly forward-- then hopefully your speedo cable will slide forward enough to attach.
Lawrence