what are you even asking?
blasters pistons stop at 68.25 you saying the bore is already 68.50... so blaster pistons are out of the question. you mention a trinty 70mm piston, whats it for? is it the same pin height as a blaster? is it a trex piston?
if you had a trex flat top 9521P68-70mm piston in before and try to run any piston with a domed top your in for trouble.
like said above you need to send your stuff to a builder that knows what they are doing if you want the right combo of crank,piston,dome,cylinder.