yes 55 and 59 Chev are close enuff the same, both 12V [55 GMC was 6V], and any 12v needs a 12v coil - get the right one: external resistor 12V!! but if you can only find internal resistor ones, yes, bypass the firwall resister
for the 12V alternator hookup, is it a one wire or 3 wire alternator? I'd hafta dig around and find the hookup [mine is old external regulated] - someone else here must know
Bill