You want an 8mm or 5/16" feed line and at a minimum a 6mm or 1/4" return line. If you don't have that, then yes, you'll need up upsize the fuel lines-on my datsun I kept the stock 6mm feed line and installed a larger 5/16" line, now the original fuel feed is the return and the feedline is 5/16". On customer cars I just run 5/16" fuel line for streeters and 3/8" or 1/2" for the racers, depending on HP and fueling requirements.
As far as fuel pump, Airtex E2000 is fine-and they're inexpensive. Readily adaptable, but make sure your line from the fuel tank is at least 3/8" diameter and picks up near the bottom-you do not want to run the inlet dry nor do you want to have the pump trying to "suck" fuel uphill. Make sure the pump is lower than the bottom of the tank (even if it has to draw fuel up the line then down to the pump) because you want to keep the pump inlet flooded.
They're greased to protect them on the first dry start-but the fuel washes that grease out and starting the pump dry will kill it in short order. This goes for any gerotor style pump, and most turbine style pumps too.
The 240SX harness-is it the complete car harness or just the engine harness? If it's the whole car...then I would start swapping out the harness from headlight to taillights! (that's part of what makes the truck harness soo good too-all the wires are long enough or too long for just about anything.
It's only the engine harness unfortunately
Have you tried installing with the stock mounts yet?
I haven't gotten to install anything yet. I have 2 more weeks at my apartment where I don't have space tools to work on it, so it's sitting for now, i'm just trying to gather as many parts as I can right now.
One more question. I was told that with a SOHC KA using a 240sx harness, you have to use an auto ECU if you put it into anything other than a 240 or else you get a 3k rpm rev limit. I've never heard this before, can anybody verify?