here's a good start to understand '70 Lynch Rd. (or an assembly plant in general)

building the Superbird up

the gate/base number refers to the fixtures at the plant used to construct the uni-body

different plants did some things in different ways
Lynch Rd. used the last 3-digits of the 7-digit "ENGINE/TRANSMISSION/AXLE assembly part number" on their fender tags, this same info is on a broadcast sheet

N = 383 4bbl (& is included as part of the VIN)
E63 = 383 4bbl
xxxx 089 = orange engine assembly for B/E-body - 383HP 4bbl (335hp) with A/C & Holley carb. for automatic transmission
or
xxxx 088 = orange engine assembly for B/E-body - 383HP 4bbl (335hp) w/Holley carb. for automatic transmission
etc.

side-gates.jpg