Help! Intermit. starting problem!!

I have taken regulator off to find out which one I have for rplacement. No number, parts store wanted to know how many ceramic on back? I took cover off and is solid state. Resistors and 1 transistor. I then sanded the mounting points to remove paint for ground, also sanded and cleaned all mounting points and connectors and battery post again. Put all back together and I had to jump at relay 1st time then it would work ok for a few more trys.???
Question: How do you tell which voltage regulator to buy? I have a 1967 Dart with a 1970 318, Alternator has been converted to 2 field wires and has a part number Duralast DL 7509DP Twin Pulley, UPC # 05294860718.
I guess the regulators come low & high ohms????
Will go down and try bat test first just grabbin lunch here and thought I would ask and try to buy one while testing Batt.
Thanks again Guys, your all great!!!!!!!!!!!!