gmc cabellaro v6 - v8

help! Thought this would be a straight forward swap. took out the blown 200 v6 from a 79 gmc cabellaro and tried to set in a 305 chevy 84 into it. the moter mount holes do not line up!~!! Do I simple place the engine in where it should be, mark the holes pull the engine out drill new holes then simply bolt themn on.??? Simple project car for my boys first time , i thought, but this is the only problem we are having. Yes we already have a new transmission turbo 350 for it. Wanted a 350 engine but all the stock car racers in iowa eat em fast. Kept economical fo a low milage 4 barrael 305. any help appreciated.

Go to
http://www.jagsthatrun.com/Pages/AstroVan_V-8.html

or http://www.astrosafari.com

they have some V8 swap info