The TRC-457 was the top Navaho at one time in '77 and '78 with the TRC-458 Navaho being the next one down. The TRC-490 replaced the TRC-458 after that. They look exactly the same but have different boards. There was no replacement for the TRC457. The 457 and 458 along with the mobile 449 all had the 858PLL Uniden PC-196BD board. In 1979 Uniden switched to the 8719PLL PC-385 board which the 490 has. They are all good radios. Many of the other brands such as Cobra, President (which were later labeled as Unidens), Robyns, Teaberry Stalkers, Couriers and others all went through the same change as they all used the same Uniden boards.