I thought this was pretty clear cut, but apparently it's not... I went thru about 50 build sheet copies for Mach1's I had filed , here's what I came up with:
Wheel size (Fields E7,8) 60 means 6" rims, 70 means 7" rims
Plain Steel wheel cars have "R" under style (E10), "S" under type (E11), Color (E9) and Code (E12) are blank
Styled steel wheel cars have "A" under color (E9), "S" under style (E10), "A" under type (E11), and "A" under code (E12)
Type of hubcap isn't shown on the build sheet, but it's specified in the spot 65 of the vehicle order image (that big long number across the top of the marti report)
"9" = styled steel wheels
"V" = trim rings / hubcaps
"3"= Sport Wheel Covers (This is blank on alot of Marti reports)
What I found:
All "Q" and "R" code cars have 7" rims and F70x14 tires
Most "H" and "M" code cars had 7" rims with either the standard E70x14 or the optional F70x14 tires ($29.00 option)
However.....
I have one buildsheet for an "M" code car with the optional styled steel wheels, E70x14 tires, and 6" rims. This is the only buildsheet I have for a Mach1 with 6" wheels. I also have one buildsheet for an "H" code car with styled steel wheels, optional F70x14 tires, and 7" rims.
Not quite related, but I also have 2 "H" code Cougar buildsheets that have cars with F70x14 tires and 6" plain steel wheels but they may not be "Competition Suspension" cars so it's not really relevant.
Hope this helps, John