For sure an early 1948.
One of the very early Pacemakers and is easy to identify because of the "gussets". Only the very early frames had the "gussets" and the bicycle type seat.
The "loop" frame was used from 1948 to 1950. The 1948 & 49 used the "J" motor [a few very early bikes were rumored to have the "H" motor]. The 1950 had the "300" motor, short breather, aluminum exhaust manifold, and the 5" rear brake. It is also important to note the 1950 "300" motor was different than the standard production motor, as the area below the flywheel was short like the "H" motor. In 1951 the "loop" was removed from the frame. In 1952 the "700" series motor was used. All Pacemakers from 1950 to end of production used the 5" rear brake.
The hardest part to locate will be the chain guard [sadly I traded my spare to Fred White].
The front forks are also different on the 1948, and use a different "bumper" and don't have the flange on the fork legs to affix the front fender braces.
Memory Lane should have the correct fenders & braces [you can use the rear fender from the 1951 Ambassador if you can't locate the correct fender].
Although the tall oil breather isn't original it is considered "correct" as it was an upgrade offered in the early 50's, and simply allows the motor to hold 8 ounces of oil [stock was 6 ounces].
I have a 1950 Pacemaker, and is by far the best riding motorbike in my collection [over 25 motorbikes].
I have approx. $100,000.00 wort of vintage NOS parts if needed, and can advise where to find just about any part you may need.
The correct paint is 1984 Ford "midnight canyon red" [Whizzer maroon]
Hope this information is helpful.
Have fun,