I looked into the same issues when building my stroker. Crower could cut me a custom crank for about $5000-6000 a couple years ago, Scat wouldn't even talk with me.
I decided to go with a stock LD28 crank with 240Z rods and had minor clearnce issues with the connecting rods hitting the bottom of the cylinder bores. Had to relieve that area a little bit. I would assume a longer stroke crank would have more issues with bottom of the cylinder bores, but if you use custom rods with a smaller journal size on the big end, you might be ok.
I am no expert and am just relaying on info that I gathered. There are more knowledgable people on this board than me.
If you are more concerned with HP than "WOW" factor, I would look to the JDM guys and replicate their builds or what others on this board have done. If you are building an unlimited budget show car, then more power to you and be sure to post a build tread, the community would appreciate it.
Remeber, just because someone hasn't done something yet doesn't mean it can't be done. It just might not be pracitcal.