At this point in the process I had a running car for $3,500 and the next step was to address the safety items of cage, seat, belts and harness etc. The rules are pretty exacting so I suggest you go to the SCCA and download the latest rulebook for the details as I do not want to miss anything critical or cause you to miss the latest update. The GCR can be downloaded here: https://www.scca.com/pages/cars-and-rules
Before you install the cage you obviously have to remove the seats and headliner, but it is suggested you also remove all the interior items allowed by the rulebook. B-Spec is much more limited than most other classes, but it also has some flexibility with regards to requirements. Door windows are a great example, they may be removed in order to fit a proper NASCAR-style door bar, but its not required. We made the decision to leave them in this car so we do not always have to cover it outdoors or always transport it in an enclosed trailer. It you make the same decision, please consider these drawbacks; it limits the space for the cage's door bars and the further they are from you, the safer. Plus it adds weight and worse, its in the wrong place. Cage design is critical, if its your first cage please contact others with similar cars, look at the designs and ask alot of questions. The nuances are critical. A friend has a Mini and does endurance racing, so they made a decision to have the door bar lower than normal to facilitate driver changes. Our other Mini has a lot of diagonal bars which are great for stiffness, but seriously limit the amount of spares, tires etc that we can carry in the car when its trailered. And finally and perhaps most importantly, the cage builder/welder is an important consideration. If they build circle track cages are not used to SCCA-type cages, they construction method may make you run afoul of the rules when it comes time to get your log book. You can expect to pay $2,000-2,500 for a top notch cage, although finding less expensive cage builders is possible. Or you can do the work youself provided your welding skills are on point and you have all the necessary tubing benders and notching equipment. We also joined a few friends building cars at the same time and got a quantity discount from our builder because he was able to order the material in bulk, and measure and cut multiple cages at one time. Including the fact that we had to replace the sunroof with a metal panel, we were in for $1,000. A quick note about cages, please make sure to disconnect and remove all possible electronic boxes and the battery so you don't accidentally fry them - that can get expensive.
A proper race seat is the next most expensive safety item, with great entry-level seats going for $200 and great full-containment seats going for almost $1,000. We have always budget shopped seats and have often purchased used seats to save money but after our friend David's horrific accident at VIR (he is fine but the car was not) we will never race again without having a full containment seat. We built the car with a used seat we had already that had a roughly $150 value but it now has a full containment seat. I would budget $500 for a proper seat. NOTE seats should be purchased based on your fit - they come in different widths so get one that fits snugly and we highly recommend test sitting before buying. You also need to budget for a seat back brace as required by the rules. There are expensive adjustable systems and even fabricating something yourself will require materials and time. In our case we were able to use parts we had on hand but figure $50-100 for this item.
In addition to the seat you need belts/harness, window net and we recommend a proper wide angle mirror. Belts can be 5- or 6-point and because their designs are different in terms of how they attach, their lengths etc, they range from $150-300 from any number of reputable sellers. We went with a $200 set from Summit Racing because we have seen videos of mail-order belts snapping in accidents. The window net and attaching hardware was another $100. Don't forget an area that is often overlooked in budgets, the seat and belts must be attached by the proper grade hardware, so figure another $50 for those items and $50-75 for roill bar padding. So we have $925 in these safety items.
The final area to look at is the requirements for fire systems and kill switches. B-Spec cars do not require a full fire system, a bottle is sufficient. And kill switches are recommended but not required. If, however, you want to eventually race your car in different classes, some of them require a kill switch so we would recommend it. Our car used a fire system we had in another car and we decided to not install a kill switch. You can figure $50-100 for a fire bottle and another $35 for the proper metal clamps (most extinguishers come with plastic clamps which are not allowed).
In the end between cage, harness, fire extinguisher etc we have now added $2,100 to our $3,500 car for a budget of $5,600. Here is Part 4 Finishing the Car with the Fast Bits. https://www.b-spec.org/blog/part-4-building-a-pole-winning-b-spec-car-the-fast-parts
