Got the one Pelican Parts catalogs for a 75 914 but the big port is 12mm.
It needs an 8 and 9mm port to match the lines on a 74 914.
I think Clay listed an Airtex part number?

@clayperrine

5/16 line from tank to pump.
Pump to filter line diameter is based upon the filter
Filter to tunnel line is based upon filter and tunnel line
Line from tunnel back to tank is 5/16

So, you can use the filter to change diamter

I use an Airtex E-8445. Same pressure and volume specs as a stock 2 port pump. 5.16 in and out. Available from FLAPS.

I have one on Betty's 914, and on the big six. It works great in both applications. And I keep one in the trailer box with a long set of wires and some hose. If we are somewhere on a trip, and the SUV is running really low on fuel, we can transfer the fuel out of the 914 on the trailer into the SUV. It gives us a 16 gallon emergency reserve so we don't get stranded in the middle of nowhere. And if the pump breaks on the 914, we have a spare.

Bruce,
I have 2 nos 3 ports but the bottom port is the larger version