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At first glance this does indeed look like a first order Tyre Frequency related vibration (T1)
More information on orders and harmonics can be found here
However we may have other issues which I will come to in a moment
Sticking with T1, your RFV of <50 Newtons is great, and so we can assume rim and tyre run out, deviation etc. are ok (The following video from Hunter explains RFV perfectly
If wheels and tyres are OK, then we need to focus on "zoning" into the vibration by re-positioning your accelerometer. If you have 2 accelerometers keep the X Axis attached to the drivers seat and measure the X Axis at each corner of the vehicle as we have here in this video
Moving on, click on "Add Vibration" and select Engine Speed Vibration 0.5 Order.
You can see below that a 0.5 order engine vibration also coincides with your T1 frequency and this could be responsible for your vibration
Please click on the E0.5 label in the Frequency view to read more about E0.5 vibration orders where the largest offender is often a misfire (combustion anomaly) A V8 will carry/disguise a misfire quite well