John,
If you have "several" of the short tubes, cut an inch out of one and weld it to another to get your length. Easy peasy.
My '40 had low oil pressure and I fixed it by emorying the bottom plate like so with 60 grit paper. The dark points were leaking. I took it down to where these were gone, and a THIN layer of RTV around the edge.
I also put a 3/8" nut behind the pressure relief spring, which is an old trick we used in the '60's at the car dealership I used to work at to raise the pressure.
She now runs 40# at cruising speeds and 20 at idle when hot.
Mike in Colorado