Will a speedo cable from a 87 360 with a B200E fit a 83 360 with a B19E?

The only difference one has between cables, besides LHD and RHD, is the connection to the instrument (VDO or Smith).
Any difference in thickness of the cable at the hub can be overcome changing the "plug" (in which the cable ends) in the greasecap as well.

They said theirs was the "small speedo" would i be correct in presuming as mine is 87 mine would be different?

Not sure what they mean with "small speedo", but an 83 car will definitely have a Smiths speedo and an 87 car a VDO one. The changeover was some time in 1985 (the last "MkII" model year, with the smaller bumpers, smaller rear lights, non-bonded rear window).

Cheers

Tom

Thanks tom

I have a new genuine Volvo smiths speedo cable if you need one

Pm me a price and I'll pass it on. thanks.