I have a 1999 v6 base automatic mustang. I swap the feul pump as well as spark plugs and battery and crankshaft position sensor. The car will crank perfectly fine but will not turn on what else can I do. I have fuel pressure. But still won’t turn on at all.
There are a few things a car needs to runs. It cranks so that's a start. There are 5 things it needs. Fuel, Air, if the filter is bad you wont be able to get air into the engine to start. Spark, get a spark tester to make sure the wires are working properly. Compression, if you have bad compression then I don't think it will be worth keeping the original engine, unless you want to pull it and make sure you don't have any cracks in the block and rebuild it, or you can just swap it and have some fun. And timing, check the timing belt and make sure it has proper tension and hasn't slipped any teeth throwing off the timing. If you want a proper guide to checking everything check out this video that goes into detail about everything I just mentioned.
View: https://www.youtube.com/watch?v=PNhuDCVIydw&ab_channel=ChrisFix
If this were my car the first thing I would check are the ground wires (black with white stripe) that go around the battery and connect to the radiator core supports.