I went through this decision-making process after doing a search on coolant on this forum and decided to go with the Cat ELC in my '99 PSD here in North Carolina. It looks like a good product and I like the product effective lifespan.

Also, you might want to look at Gooch's coolant flush write-up here: Ford Super Duty Coolant Flushing Procedure | Superdutypsd.com. As he says, the PSDs came with either the green coolant which requires monitoring or the Ford gold coolant. The big deal for changing coolant types is to do a very thorough flush of the system before putting in the new coolant.