Were can I look to find some info about a Roll Bar/Cage requirements for Convertibles. I am most curious about bolt in/swing out door bars. I am not looking to go Professional Racing just to be able to run faster and safer at Open Track/Day Events.
The speeds that experianced drivers in well-prepared cars see at track day events is indistinguishable from race speesd (and sometimes it can be faster, with no traffic,) so keep that in mind if you ever are tempted to "save" on a cage, and ractionalize it by thinking "it's only for track days."
If it were me, I'd find a local cage guy who builds for NASA or SCCA. Avoid NHRA-type cages. NHRA rules require the cage to have some features inapproptiate for road-racing. Then talk to them about what you want and need. Personally, I'd build the cage to NASA specifications regardless (SCCA would be OK too, I'm just not as familiar with their requirements.)
NASA now requires NASCAR bars (at least in AI -- I'm not sure about CMC.) that may be over-kill, especially if this is still a street car, and if you want removable door bars, it sounds like it is. If you do opt for removable door bars, keep in mind that that will be a BIG compromise, safety-wise. Do as much as you can to keep that area strong by using big, beefy hattaching hardware for the bars. Bolts/pins won't be enough.
There is an EXCELLENT thread on cage design over on Corner Carvers.