vauxhall brake conversion

A few years ago I collected all the parts needed to do a 280mm front brake conversion using Vauxhall calipers, however I sold it all on. I am now thinking about collecting the parts again ( so much cheaper than g60 calipers and adaptor brackets) but cannot remember which calipers to go for and size of shoulder bolts, can anyone help. Have seen the guide on here but that appears to be for 256 mm conversion. thanks