Is there confusion, here....maybe a bit.
Facts:
Z16 has been used three times to my knowlege. The 1965 Chevelle SS396 was RPO Z16. The 1996 Grand Sport (cpe and conv) was RPO Z16 and the 2004 LeMans Commemorative Edition Z06 was RPO Z16
Z18 was an European-export-only, LeMans Commemorative non-Z06 Coupe (ie: Targa) which had the stripes (but w. different dimensions as noted above), the CF hood, the red brakes, but lacked the Z06 tires and wheels, the LS6 engine and the ti exhaust. As stated above, the wheels were the base, high-polish wheels and the tires were base sizes, but non-EMT. Information above states 45 of these Z18 coupes were built but the correct number is 46 sold.
Speculation:
My guess is the suspension was a unique crossbreed of Z51 with the Z06 shocks added but I need to look into that.