Mark........you do realize yer oil pump is part of yer #1-bearing cap, don't you? To gitt to yer #1-bearing, you haffta drop yer castiron oil pan. This is NOT a simple inplace repair. BIGGEST cause of low oil pressure is WORN engine crankshaft bearings. While Ford in 1939, specified 30wt detergent oil and 40wt for HOT weather operation; they also recommended adding a quart of kerosine for COLD weather operation. Modern MULTI-WEIGHT oil so much better. Me? I recommend 20-50wt oil. This is 20wt oil with temperature sensitive additives. You might also try 50wt RACING oil to improve yer oil pressure.
BTW, the change in oil pressure with temperature is NORMAL. Its called "viscosity factor". ........oily Dell