The Fiat 1500 from an X 1/9 is a pretty simple swap from what i hear. having just purchased a '89 GV, it is the route that i am going to go with it. I'll keep you guys posted on the project. me and my little bro are picking the engine up this friday, so wish us luck!
p.s. check out the Grassroots Motorsports website, grmotorsports.com, for advice and parts...the people there really know what they are talkin about