IMO if it's mainly a street car don't put a roll cage in it, the proximity of the bar will most likely result in a head injury in any accident. There has been a lot of discussion on both the Pantera and GT40's forums as to the risk of roll cages in a small restricted cockpit and most would agree it's not recommended.
If you really want something consider a 3 point roll hoop that sits behind the driver against the firewall, most vendors sell them with a removable third diagonal member that bolts into the passenger foot well when required. If left in it is restrictive to a passenger.
Julian
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