I don’t know of anybody installing one on a Frontier.
I do have friends that installed them on there early generation Dodge diesels.
The reason, with 4:10 gears the early diesels did not rev. With the “Gearvendors” splitter it allowed for lower rpm at highway speed.
Since then, they purchased later models which made the splitter unnecessary.
I don’t think it would be justified cost wise on a early model Frontier.
A ”Gearvendors” splitter is close to 3 grand, plus the cost of installation.
I can see spending the money on a vehicle worth forty grand, not on a vehicle where the cost is equal to the value of the truck.
Back when, I installed a 5 speed overdrive tranny out of a 2.5 ton truck in my 1983 Ford diesel. Worked so so. Should have gone to a splitter.