CARTER SEEKING BILL TO THWART BOYCOTT
Mar 1: Sec Vance says Carter Adm has reversed Ford Adm's policy and will support passage of law barring US cos from taking part in Arab econ boycott of Israel, testimony before Sen Banking subcom; says Adm does not favor either of 2 anti-boycott bills before Sen and would prefer drafting new legis in cooperation with Cong; lists 7-point set of principles to govern such legis; says that so long as legis deals only with secondary and tertiary boycott issues and does not infringe on right of Arabs to boycott Israel, it would be understood by Arab leaders; says Arabs have right to control source of their imports (M)