Rob,
Before shipping anything back, I'd go through the exercise of getting them in the car. The wire diameter might be close,
but the steel spec can be different, ie; stiffer, looser, etc.
The old ones from my car hit the trash bin in 1996. I should have saved them, but someone had already changed the rears
to a cargo-type overload spring, so I didn't have original rears. The fronts were pretty worn out, but I should have saved one.
I bought front & back springs from the GSCA in 1996, and they were in the car until last year. I don't know what they sent me,
but the car sat about 5 inches higher than stock, even with the engine in. Right now, with the ESPO springs in, it looks good -
a little higher in the back actually than what I would like, but I still need to get to get some glass, interior, etc. in the car.
Pat Guida put ESPO springs in his 4 speed convert as well, and was very happy with them.
Mark