400 stroker cranks

Looking to build a killer street, pump gas stroker motor for a big tire light car.
Most all kits listed for the 400 seem to max out at 4.25. Has anyone crammed a 4.375 or 4.5 in a stock block?
If so how hard was it to do and was it worth it?
Was there issues with finding pistons off the shelf or issue will rod length and availability?
I have searched the internet and could not find one thread on this subject. Any help would be great.