Too cold to start car

I'm guessing most of us don't drive our cars much during the winter months, but occasionally I like to take mine out on a sunny day even if it's only 25 outside. Problem is, I just can't get my car to start when it's this cold. I tried for 20min yesterday before killing the battery and my jump box. Didn't try any starter fluid, didn't have any on hand. When it was warmer out, I don't have any issues. Yea I know, welcome to the world of carburetors.

So, I was just wondering if there's anything I can do to make my car a little easier to start when temps drop below freezing. Ok, I mean "reasonable" things, I don't want to put on an EFI system. I will mention that my carb has no choke. I bought a kit from holley but ended up having to replace the main body on the carb which the new one (from craigslist) turned out to be slightly different and the arm to the choke doesn't fit right.

Extra info:
'73 Duster 440, DB electric mini starter, msd coil.
Hi, I have a 1973 Dodge d-200 pick up... with a manual choke that I installed... and in the winter I keep an oil pan heater stuck to the bottom of my oil pan for fantastic, easy starts... I face the handle part forward with the cord and the heater has really strong magnets that keep it on all winter. I pull the cord and plug forward, secure it with zip ties and keep an extension cord run out to my parking place. If it warms up, I leave it unplugged. They sell dip stick heaters, but not in the size I needed and the pan heater was only about $40 and is now on it's 3rd winter with no trouble. Maybe this will help if cold is the problem.... otherwise a battery minder to keep a full charge, but I don't need one.