Correct spark plug wiring diagram

google the engine make for the firing order
p0300 is random misfires and is seldom plugs and wires but more likely to be low fuel pressure ( dirty filter) or blocked injectors

18436572 going clockwise starting with the post facing the number one cylinder if the distributor is placed correctly.

As far as I know, all chevy 350s are the same.

1-8-4-3-6-5-7-2 Distributor rotates clockwise vehicle , #1 cyl is on left side of engine

check the ignition modual under the dist. cap

This method is good for the firing order on all chevy small block v8 engines from 265 cubic inches to 400 cubic inches. This would include 265, 283, 305, 327, 350, 400 cu. in. chevy small block v8 engines.

Let's cover some safety concerns first. If you try to troubleshoot a mixed up firing order with the engine running, you could be in for a serious shock,.. literally. You can do it, with certain precautions, but you really don't need to check the firing order with the engine running. You definitely don't want to try checking the firing order if you are wearing any kind of pacemaker or sensitive electromechanical prosthesis. The voltage coming out of the ignition coil is in the thousands. Common sense dictates that you wouldn't stick a knife in an electrical outlet, so you wouldn't want to take chances with being shocked by the electrical discharge from your classic chevy's ignition coil either. See the diagram:




The firing order, which should be cast into the intake manifold, for the chevy small block V8 is 1-8-4-3-6-5-7-2. The firing order is the numerical sequence in which the spark plugs are fired. The insertion position of each spark plug wire around the circumference of the distributor cap can be found according to a clock face. The insertion sequence determines the firing order. The firing order is followed clockwise around the distributor cap starting from the 6:30 position with the 6:30 position being the number one cylinder spark plug wire.

On classic chevy small block engines that use ignition breaker points instead of electronic ignitions, the number one cylinder is the one immediately clockwise of the small metal sash cover on the distributor cap. The firing order starts here. There is no sash cover on the distributor cap for GM HEI electronic ignitions, and the firing order is the same, but starting at the 5:30 position.
The firing order makes sense if you know how the cylinders are numbered. The number one cylinder is the front most on the drivers side and 2 being the front most on the passenger side. From front to back, the cylinders are odd numbered on the drivers side, and even numbered on the passenger side.

Additional details HERE.

Hope helps (remmeber rated this).

Firing order is 1-8-4-3-6-5-7-2 and the rotor turns for clockwise. If you look at the distributor cap the Above

1-3-4-2
Marker on dist is number 1 (TDC) next with correct rotation of the crankshaft should be cyl 3 and so on. The corresponding firing order should have a TDC orientation meaning during power stroke the valves should be both closed. Same at the dist cap 1-3-4-2 in the correct direction of rotation.

Hi,
I don't know your engine size, but the link below is a picture of the GM small block firing order with distributor.
The firing order, which should be cast into the intake manifold, for the chevy small block V8 is 1-8-4-3-6-5-7-2. The firing order is the numerical sequence in which the spark plugs are fired. The insertion position of each spark plug wire around the circumference of the distributor cap can be found according to a clock face. The insertion sequence determines the firing order. The firing order is followed clockwise around the distributor cap starting from the 6:30 position with the 6:30 position being the number one cylinder spark plug wire.

http://www.classiccarauto.com/impala/how_to/images/distributor.png

Hope this helps...