I have one of the first Firecore distributors in my Savoy and it's just a mag pick-up tall model for RB engines. The advance is easy to adjust with just a Phillips screw driver to loosen the plate. Mine came with about 15* advance and the springs were perfect out of the box for my car. I had to adjust the advance to 10* and it was easy on a big block. There are no measurement tools that I am aware of though I just set mine and checked it and got lucky on the first try.
I am very happy with mine and I suggest you leave the springs alone or change them without disassembling the distributor. I changed them on other Firecore units using dental picks and micro needle nose pliers. This distributor is not really meant to be disassembled and the only ones I have seen troubles with are those that have been disassembled to change the springs.
Mine has been flawless for almost 8 years now and I would buy another one if I had to.
You can get them with either type of cap so make sure you specify with your order.
Gus