Ground strap composition
As an FYI in my field of professional expertise aviation maintenance, all the grounding straps we use on aircraft are bare fine strand braded wire with crimped on ring terminals. This is for durability and reliability. Lots of vibration, and on such things as flight controls and landing gear doors which have grounding or "electrical bonding" straps on them, these components are always in movement. A fine wire stranded braded cable allows very good flexibility with low issues of breakage.
Typically when changing a bonding wire, you have to do an ohm check from the bonding wire to the adjacent structure next to it but not touching it to make sure your getting a solid connection. The main reason for the grounding wires is lightning strikes. If the whole external structure is electrically connected or bonded including moveable parts, when its struck by lightning, it will absorb the charge which will travel through the structure and exit out through the static dischargers (little antenna looking things on the back edges of the wings and wingtips) with minimal burn damage to the structure. Without a good bond I have seen stuff like composite wingtips burnt and charred off !!! This being said that's a lot of voltage that jumps through these bonding wires. Using a fine braded uncoated bonding wire for a body to engine ground on a car is a far superior way to do this.
Now back on topic, my 67 cuda came with a black insulated 12 gage wire with ring terminals at both ends as a ground. It appeared to be stock. I will be putting bare braded wire instead from the firewall to the back of the block. Also going to jumper a second braded cable from the motor mount plate on the engine side to the K frame as a secondary motor to body ground. My firewall ground I plan on using a steel riv nut or nutsert on the firewall for a 10/32 stainless screw and the braded cable. This will make sure I get the best ground possible with little to no degradation.