Mk2 rs pre custom

[Class1010]

Hi does any body know the exact details of the pre custom compared to the custom, would I be right in saying the broad strip came out in 76 the pre custom in 77 and the custom and base model custom in late 77 to 80, I have a pre custom Feb 77 with roll top seats sort door cards it has the clock fitted in the dash is there any thing else differently done ? Thanks for any information