A 1500 would normally have a cable operated throttle, as would a Mk4. Mechanical linkage operation was used on the earlier roundtails (Mk1, 2 & 3). I actually prefer it, owning both types, but this is personal preference.
The kangarooing is not just limited to mechanical linkage if it's induced by your foot moving the pedal when going over bumps, that would happen with cable as well. But what does sometimes happen is that when the engine moves on its mountings (maybe going over a bump) the "solid" linkage between carbs and pedal pivot point on the body causes the throttle to open or close slightly. That is what usually starts off the kangarooing, then your foot takes over. You do not get this with cable operation, obviously. It's something you learn to live with - changing to cable is quite involved unless you have a spare cable operated car to raid all the bits from.
I'd stick with it unless you are really unhappy with it.