That's of a similar age to my 25. It had a remarkable ability to limp home regardless what failed. (says he, tempting fate!
)
As Chewy says, PTT is not essential, you may find if you pop the lid off the emergency start pull cord is in a compartment on the underside of the lid. Worth having a try at starting manually in the calm of your local marina, rather than discovering your battery has died as the local ferry is bearing down on your fishing drift!
The good thing about engines of that vintage is that once they are running, they don't need the battery to stay alive.
Also work out what you will be doing with it. I know people who carry full tool kits and tons of spares, but to use a totally silly extreme example, what is the point of carrying spare piston rings when you need to dismantle the entire engine to change them. If however you are bouncing from beach to beach and threre is a local bus service, worst case you row / limp to the nearet beach / marina & get the bus back to fetch your trailer.
As a wee example, the last failure I had on my Suz was the throttle sensor. £150 worth of electical gubbinry that would fit in a matchbox. I posted here, and it looks like I have the only one in Britain that failed! It was also a fiddly pain in the @rse to fit (whole oil tank had to be removed) & calibrate in the warmth of my garage, so what chance would I have had bobbing about on the Clyde hanging over the back of the boat? It's a rare example, but I use it to illustrate a point. (e.g a spare prop is fine IF you can get ashore to change it)
An aux and a toob patching kit would be a good start.
) DT60 was basically the same motor (and very early DT65), if you're looking for spares 
