sounds like you have a 4 cyl gasser 62-64 prior model 2000, as the diesel 62-64 was 12v already, and all 3 cyl jobs were 12v.
so that means you have a 6v gen and reg.
2 easy options.
buy a 12v gen and reg for a diesel 62-64 prior model... or buy a delco 10si 3 wire alt.
the 12v gen / reg are direct swap outs.. just buy a napa ic14sb coil to replace your 6v ign coil.. and get new lamps.
if the alt.. there is a tisco kit for brackets.. or make your own.
on alt setup, run charge stud to the wire on the old reg that was labeled bat.
the alt has a lil 2 prong slot.. labeled 1 and 2
make up a jumper wire with a spade connector and ring terminal and connect 2 to charge stud.
make up another wire and run from 1 to the ignition switch.. but buy a lamp holder and run the wire connection thru that lamp holder. lamp should be a 194 lamp.. like a trailer marker.
ie.. wire from alt 1 to one side of lamp holder, other side of lamp holder to same wire on ignition switch running to coil.
key on = lamp on, once you start and get over 400 rpm or so, lamp goes out and chargig starts.
that easy.
ps.. get correct pulley on alt for belt.. etc..