Wanting to upgrade my fuel pump while doing my engine and transmission swap. Been researching and it's making my head spin. I am more than likely making it more difficult than it needs to be.

I am thinking about a trusty walbro 255 with a racetronix harness. But am unsure which harness I need. Is it this one?

Racetronix - Pump Wiring Kit MP150/280, Walbro CK* - Kit Configuration Page

My other option is a replacement AC Delco pump assembly from a flex fuel truck. (2002 VIN code Z) Is that a worthwhile upgrade? And is it a direct drop in with no mods required on a non flex fuel truck?

I am going from a tired 256K mile stock 4.8 to a low mile LQ4 with a cam, NNBS intake, 85mm TB, 8.1L 31# injectors, LT headers, full exhaust system. I would like adequate fuel supply so that I am able to beat it over the head with a 100-150 shot in the future.