Is it not possible to run off the shelf Pistons I have seen advertised? If I run the head and crank can I run after market Pistons designed for this application?
I agree with Beater - sometimes it is cheaper to start with what is in hand - especially if it is known to be sound. And they are heavy bits so shipping just piles on to the cost equation when shopping for an alternative.
As for pistons if you bore and stroke a 228 you are likely headed down a path toward custom pistons.
Old GMC Trucks Page 
The 228/248 blocks are shorter then the 270/302 blocks - but they use the same connecting rod length. So the piston needs to be crafted with the pin closer to the top of the piston to compensate for the shorter deck height.
With custom pistons you can have the block prepped and measured - and then order slugs that are an exact fit.
regards,
stock49
