Are you after looks or HP . I would go supercharger for HP and the looks and sound .Either way you have to get a full rebuild , by the time you rebuild the 289 ready for supercharger a 347 will be around 1000 more . Either way both will need new heads ,by the time you do the old ones up fully you can buy alloys off the shelf . So there wont be much difference in price . HP for 347 will be around 410 plus maybe ,289 blown around 450 .The supercharger is where the money will be and the extra cost of a blow through carby setup . Dont forget the rest ,trans,exhaust ,diff ,radiator etc . So end of the day both engines will cost about the same plus supercharger .