you can pick up the navigator engine for 4000 dollars brand new at
http://www.dssracing.com/web_specials.htm, you can also purchase 351w long blocks with even more power for around the smae price at the same site. they are very reputable in the ford world and build very tough motors. the navigator block is tough but it will not put out the power that a 351w based stroker will put out. also, you have to take into account of all the additional cost of retrofitting the navigator engine to your car. windsor motor will definitely be the cheapest, easiest , and most bang for the buck way to go.