Here is a link to Joe Van's 'Stow-Away' 1975 Chevy outta Florida. Has a swapped in big block.http://floridavancouncil.com/cover_van/joe_van/joe_van.htm
Also, 'Utopia' has a swapped in big block, but I can't locate a pic of it.
I have an old Van magazine from the 70's that shows a big block being swapped into a 70's Chevy van. Was basically a bolt-in.
As for a floor shifter, the only one I have seen on here is in Jonny O's Dodge van. Think it's a B&M unit mounted on the floor. Brad