Sorry Earl, the car still has to pass tech inspection. That means roll bar with approrpriate guage tubing, scattershield, on-board fire suppression, kill switch, fuel cell, etc. SCCA doesn't make it easy: you have to pay just to see the rule book (or borrow one from friendly Cobra owners). It does not require a full cage.
Every race car requires a logbook. The logbook includes the inspection of your car (and sometimes safety gear like helmet, suit, etc.) For both SCCA and NASA, you must have a logbook for the car. The other thing that a logbook does is document the racing history for your car. For Vintage classes, the logbook serves as documentation that car was raced in a particular era. Some niche races only allow cars to run where their logbooks showed that they ran in a particular race (like, say, the 1965 Le Means). Logbooks can go a long way to helping a collectible car preserve or increase value. Of course, a logbook for GT Pinto only helps prove that you, in fact, have a GT Pinto.
Keep in mind, you don't need logbooks to go to NASA's HPDE driving schools. You cannot, however, go to SCCA licensing school without an SCCA logbook.