Contacted Safetey Devices about stainless bolts. Here are the emails:
I have a 1994 Defender 90 NAS. I was wondering if it was possible to replace the bolts in my cage with stainless steels bolts?
Is there any reason I can't do this?
There is not reason why you cannot use stainless steel bolts - as long as they have a strength of at least 8.8 (usually marked on the head of bolt).