Running engine on 87 octane

[Grant Bessom]

I have plans to sell/give my 1986 5ktqcs (in an attempt keep it in the
family) to my mother.  She says that she wants to run it on 87 octane.
First off, I would want to make sure the knock sensor works; how do I do
this?  Secondly, will 87 octane be ok?

Thanks

Grant
1986 5ktqcs
urS4 soon
VA, USA