Is your cable a quick connect? if you are keeping the existing cable you need a helm that will work with it and fit the same opening/mounting holes
Teleflex is part of Seastar.....go to the seastar solutions site and look thru the Products/Mechanical steering for your choices
http://www.seastarsolutions.com/products/mechanical-steering/nfb-safe-t-ll-2/
Read the "Applications" to figure out if its for you.
Keep in mind that they may fit exactly even though they look very different.
I would suggest an NFB type helm like the NFB 4.2 Rotary
Once you decide on a model, you can shop for the specific one.
Now is a great time to check your motor for ease of movement. Old motors bind up from dry old grease at the top of the swivel shaft. With cable disconnected and motor down, you should very easily be able to swing the motor left/right by hand.
If not, you should fix that.