CUSCO, I think you've just hit the nail on the head. The alternative is to exercise the standard a/d on my 140 and re-engine with a 160 motor which, given the weight of the a/c, gives performance somewhere between a Warrior and an Archer.
The instrument fix is a standard ifr setup x2 nav/com, adf, dme (but not fm immune) 12 years and 1900hrs comes up on the current motor in November, so it doesn't owe me anything - hence this isn't as silly an option as it might sound.
So before I press the button on this I'll see if I can find a suitable arrow; either one that has been loved (with money spent on it) or one that is fundementally sound, but unloved and priced accordingly.
Any suggestions gratefully received...