Not personally but I have seen a few with big block swaps Steve Scott from the old Yahoo A100 group had a 383 powered van he raced & a friend of my neighbor built one with a 440.You most likely will have to trim some floor to fit and modify the doghouse.I have a '67 A100 van with a 318&3.91 axle,and considering a G3 Hemi swap for it.What trans and axle are in your truck? I saw your truck in the pics thread,nice looking machine.
RT