Kerby, your question is a common one. Ford did just that when they changed the stroke on some of their car engines: used shorter con rods (352s and 390s in particular). Chevy did it when they enlarged the 350 V-8 to 400 cubes.
However, hot rodders for years have been stroking all kinds of engines, and the common way to compensate for the increased stroke is to move the piston pin location upwards - half the amount of the stroke increase. So, a 1/4" stroked Triumph crank will have pistons with the pin moved 1/8" higher.
There's a name for this distance, by the way. It's called compression height. The distance is measured from the flat portion of the top of the piston (NOT the top of any dome) to the middle of the pin hole.
Since the raw forging blanks that the piston manufacturer uses are unfinished when they come from the aluminum company (I think Alcoa does most of them), the piston company can put the pin location just about any old place it wants to.
Also, the piston company supplies new piston pins with their custom pistons. These pins are almost always shorter than stock, made of tougher material, and have a thinner wall section. Lightness is what they're after.
