Aftermarket Rims?

[Doughnut]

I think the one i got are 18' do you think they will fit on the 81 320i?

Low profile tyres, and a stock ride hight will fit the wheels fine - though will look like a 4x4
Also depends on the offset, a 20 offset is desired to give a good clearance.

 

[echothreezero]

I'm not familiar with e21 clearances, so can't say. If you already have the wheels, try cthem and see. Let us know. I'd like to know what you can fit on an e21.

 

[Doughnut]

I think the one i got are 18' do you think they will fit on the 81 320i?

Oops, Thought you were the OP[8)].
same as what echothreezero said, I'm not sure about the clearances.