Best bang for the buck is the STS Team .21: http://www.racernine.com/sts21team.html
Check out the dyno results of the other STS motors in comparison to others that cost much more: http://www.nitrodynesystems.com/Engine%20Database.htm
Another great motor for the money: http://www.shengines.com/tech_data_new_pt2004-xb1.htm
Check out the dyno results of the other STS motors in comparison to others that cost much more: http://www.nitrodynesystems.com/Engine%20Database.htm
Another great motor for the money: http://www.shengines.com/tech_data_new_pt2004-xb1.htm