Robert;

Presumably your system is already a 12V system...if not, it would have to be changed over to 12V as 6V Alts are available but rare and so not inexpensive I expect. For notes on this, see: http://www.sw-em.com/Vintage_Volvo_6V_to12V_conversion.htm

One Wire Alts a self exiting and OK, but that means AMP Indicator will no longer work to indicated state of system. Normal three wire connection is preferred. See: http://www.sw-em.com/altkit_additional.htm#One-Wire_Alternator

Cheers