The aftermarket piston that I found on ebay is not suitable. The skirt would be too low and cannot be shortened etc.
So, I will talk to my engine rebuilder buddy to explore the option of plugging the gudgeon pin hole and re-boring it .025 inch lower. I figure I can manage the first part of the job; the plugging up of it with aluminium bar. I will machine it oversize and heat shrink the piston onto it.
Then I will give it to my buddy to take into the workshop and do the boring of the new pin hole at the lower position.
We figure on doing it in one piece, then dremelling out the middle to accommodate the crank small end.
But.............
First of all, I need to ensure there is sufficient room between the valves and the top of the piston. Does anyone already have some knowledge of this dimension?