Hi Marv,
Congradulation on nearing the completion of your restoration!
If you have the stock radiatior, it has a long neck. You'll need a long neck cap, 7lbs.
I believe you have 3 choices as to what cap you can use.
1. 4 eared cap from your local Napa store.
2. 2 eared cap from Moss.
3. 2 eared cap that has made in England printed on it. BCS or Healey Surgeons carries it, Moss does not.
Here's a photo of mine, from Healey Surgeons.
Cheers, Roger