Thanks for the instant ID!
OK, so Giugiaro designed the Isuzu, previewed in '66 Geneva Auto Show and Tokyo, for sale in '68.
The Fiat Dino was designed by Giugiaro while at Bertone in 1966, previewed in '66 Turin (late in the year, October) then Geneva '67. So obviously, same designer, similar look.
The Fiat 124 was designed by Mario Boano, who owned Ghia for a few years, then his own company before joining Fiat as a designer. Premiered at Geneva AS in 1966.
OK so while the original Isuzu shape perhaps preceded the Fiat Dino, the original Isuzu's detailing was pretty busy (chrome etc.) and cleaned up for the Dino. Then the Isuzu facelift then retro-fitted the cleaner Dino look.
Any explanation though how Boano's 124 looks so similar to the 117? They both previewed together at Geneva.