I think you are starting to understand this "swap" will not be cheap or easy. Nothing between the two motors will swap and you are looking at a new transmission and entire exhaust. Just getting the pulleys and accessory drives right will cost you over 2 grand... You would be farther ahead to sell that Vortec and rebuild the Buick. That will bolt back in with no issues.
Going the Vortec route will leave you with a cobbled mess that will not be reliable without a lot of money and time being thrown at it.
Mark