I think Kevco makes a 5/8" pickup tube for the center sump car pans. $59.99 but it is still necked down at the pump. I have brazed the pump where the pickup went and then bored it and taped it to 1/2 inch ID.
Kevco center pickup tube M301-1
For $259.99 or so get their M301 - 340 2 quart larger car sump pan with a built in baffles and crank scraper and gain more power there too. "It is fully equipped with a gate assembly, 2 hinge traps, multiple diverters, scrapers and a baffle. Fits all standard Mopar K Frames. Uses factory Mopar dipstick."