Yes, R8905 is the chassis number.
The
Morganville Registry run by Tony McLaughlin has over 5000 entries and I see your car is in there as a brown 1981 +8. The contact details for the past owner are there (I'll make no comment on the data protection issues with that!)
You can order a "Chassis Record" from the Morgan Motor Company at
https://www.morgan-motor.com/chassis-records/. However, at £80 for a single A4 sheet, this is a tad expensive and doesn't give you much more than the original spec and delivery date.
There is a useful article on GoMog
https://www.gomog.com/allmorgan/ChassisNumbers.html. If you haven't already found it, there may well be an etching on the bonnet hinge.
I don't know what the other two numbers mean, my chassis plate has the same ones.
