Jeff D,
I believe you are correct.
The Belvedere II had a 'thin single' Belvedere II emblem on the front fender.
The GTX cars had an emblem that was 'Belvedere II' with 'GTX' underneath.
Many racers converted their 67' GTX Street Hemi to a 67' 'RO' car, so
they could put on the low-profile hood scoop.
I believe Sox & Martin were this first to do this.
Also, for a period in 1968, the NHRA classed the 67' 'RO23' cars in SS/C and
the 67' GTX Street Hemi cars without the Hood Scoop in SS/D.
Old Trapper is a 67' GTX.
Here is a 1967 'RO' (Belevere II emblem on front fender)
'