first oil change on new-to-me duster

Im doing my first oil change on my duster. The motor was just rebuilt from eddy 650 to milodon oil pan. When i got the car it was in the car not running, and needed to be wired in. I have no specs or any information on the engine, besides that it is a 360. I got the car running and would like to change the oil to rid it of any break-in debris.
So i have a few concerns.

First my main concern is when i drained the oil, i got only about 3.5-4 quarts of oil out of it. But my dip stick read full before draining. I hadnt run the car for a few days before the oil drain. So if someone running a 360 with a milodon oil pan could measure your dipstick and send me measurements to the full line?

Next the filter on it now is a fram ph43, id like to switch to a purolator or wix. Im running headers, so i need the smallest filter i can get. If someone could fill me in on a part number for either that is equivalent to the fram ph43 thatd be very helpful.

Lastly id like some input on what oil i should run for my first 150-200 miles. I dont know what kind on breakin oil was used, but was assured that there was break in oil in the engine when i bought the car.

Also, im new to the classic car/mopar world, so any tips or advice for helping me out with this new engine would be awesome. Thankyou- Ryan