Doh!!! wtf you guy's are all behind the times this was done years ago because the crank wasn't available just go and pick a stroke you want, and build it.
Oh by the way years ago it was put the 60 crank in the 40 block (doh not the 18 block) and it was bigger and better than the 60, you then had to use a x rod i think if memory serves me and machine quite a bit off the top of a good piston (not a junk piston) and then it worked, but this was done years ago because there wasn't a thing called a stroker crank or well atleast 1 for under a few thousand, the other trick was to offset grind it and do it but i am slowly forgetting all that stuff thank god.
Just go and look for a stroker crank