Go for the Audi 5 cylinder.  It has = 130-165 hp (depending upon model), plenty of low-end torque, and no head gasket concerns.  For the moderate difference in cost, you get a = tremendous series of benefits.  After all, that's how they make them now in S. Africa.
 
Budd Premack
86 Syncro, = 84 GL(for sale soon), 73 Super
Minneapolis, MN (Land of Sky Blue Waters)