Hey Ted,
All the funny car seats were aluminum. Murf always built the seats himself it was one of the few hands on things he still did. I did the dragster seats out of Kevlar. On that year car the seat padding would be minimal only what the driver would have added. The clutch box could have been carbon or aluminum depending on what the team wanted. If you find it was carbon you may want to sand the ribs off the plastic one your using. Most likely the valve covers were also carbon as that is before they were outlawed.
The detail your putting in this are incredible. I keep thinking it is 1/16 scale the detail is so clean. I will be following this one.