"Z" engine code in '66 was the 315 hp "Thunderbird Special" 390 with 4V carb, Ford listed it at 10.5:1 compression ratio requiring premium fuel.
1966 was the change over year on FE cylinder heads, and there were more cylinder head castings used than any other year. Both cylinder heads with the earlier style tall intake ports, and with the later style short intake ports were used. Same with the exhaust port location ( higher & lower ). A couple of the more popular cylinder head castings were the C6AE-R and the C6AE-U. There were a couple different cast iron 4V intake manifolds used on FE's that year as well, although I don't know if there was system to how Ford used them.
The lower portion of the Warranty plate decodes as:
Body 57F: LTD 4 door Hardtop
Color R: Dark Green Metallic
Trim 98: Light Ivy Gold Vinyl & Light Ivy Gold Cloth
Date 28B: Feb 28th 1966
DSO 42: Fargo
Axle 6: 2.80:1
Trans 4: C6