When you send it to the pump builder, ask about him using a ford tail fitting on it, they are 3/8 inlet instead of 5/16, or drill/ tap while off yourself. even if you don't enlarge the filter outlet right now, the hard part is done and can be done later when you have time.
Also, using hard fittings, put a "T" right at the inlet for fuel pressure gauge. Again plug it for now if you cant do the gauge itself at the moment. I usually do a mechanical gauge, but this time I will do electric and put the sensor on the T, and a second sensor pre filter. then wire through a switch to read ip pressure normally then can flip switch momentarily to see when filter is due for swap. the filter due isn't really important, but knowing incoming pressure is.
Last is use a clear return line coming out of the ip with hose clamps. its 1/4" about 5" long from any hardware store. Have to replace that piece every 3-5 years, but it is a couple dollars and so easy/fast- well worth it for all future diagnostics.
Please let us know who you send it to and pricing/ results of work. knowing several pump builders is always a good thing.