Lister CS piston swap

I have a Lister CS 6/1 and I assume (engine is not yet stripped) it has got a cast iron piston (engine is circa 1950) and there is some bore wear or I assume there is as there is a little bit of blue smoke when it is running. When I overhaul it I was wondering about changing the piston to an aluminium type as it is about half the weight of the iron one (using Stationary engine parts errm.. parts) and that must be good for smoother running by eliminating all that extra reciprocating mass, has anyone done this or has anyone advice on this? There seems to be little in the way of crankshaft counterweights so assuming I have the correct piston to bore clearance I can't see much of an issue but I will heed those with greater experience. Of course in stead of mucking about I could just re ring it and leave it at that, it will still probably see me out.
Regs
Dale

You will need to also get the "bump clearance" right.  Bump clearance is the gap between piston crown and the head with the piston at the top of its stroke.  This determines the compression and is a little critical on diesels as they need sufficient compression to provide the heat for ignition.  But  normally the piston is already close to hitting the head.
So you need; the right bore clearance, the right gudgeon pin diameter and width, and the right crown height above the pin.  I can't remember, are the counterweights in the flywheels on the 6/1?  Where ever they are, they will be too heavy with an alloy piston.  
Admittedly they do only run slowly but then that means the piston weight is less of an issue.
Before you go re-ringing it, check that the oil is not too high and that the rings are not stuck in their grooves.  This happens a lot on engines that do much cold running.

Hi Dale, Darryl made a good comment about BUMP CLEARANCE when you get round to stripping the engine save the papers that will be at the bottom of the cylinder on the crankcase these make up the bump clearance like spacers,it will give you an indication to what you will eventually need.
Another point he made was about running cold engines. I have rallied and had a few CS s, I made my cooling tank from a two gallon fire extinguisher more than enough for rally speeds in fact on some occasions the water was not very hot after roughly six hours of running.
I too would look to stuck rings as Darryl says if the engine has been idle a while.
The CS is a fantastic engine that will run very well once it is set up, what beats me with them now is weight I am getting too old for them.
I will look out some pics of CSs I have had over the years. Regards Billy.