T5 into Early Fox Chassis

Do you mean SROD? 4-speed overdrive trans? If so, the speedometer cable will work - converted an '83 5.0 Capri w/ SROD to T5 and used the stock speedo cable.

If it's a completely different issue altogether, you might want to try to just get a new speedometer cable from a T-5 equipped car. It should mate to your speedometer just fine, and then there will be no kits or worries. Parts are available in junkyards everywhere. I think the C4/AOD cables might work too. Just make sure you have the right driven gear (gear at the end of the cable) for the rear end ratio you have.

JS