My car currently has an 8 point roll bar.
I only run 1/8th mile only. The car ran 6.70's for about 10 years.
I built a new engine last year and it ran mid 6.40's to low 6.50's during the year from cool to hot air.
So ET wise it doesn't require a roll cage.
My question is even though it doesn't need one are there any advantages to put a cage put in, are there any disadvantages.
Just try to figure out if its worth the money or should I just keep running what I have.
If it matters have no plans in going any faster anytime in the future. Also have owned the car for 20 years and there is zero chance i will ever sell if that is a factor.

no advantage unless you plan to run sub 6.30 which the rules then mandate a cage. Disadvantage is lighter wallet, more weight which equals slower ETs.

The fact of the matter is the right way to do it when you need it is to remove your 8 point bar and start from scratch with chrome moly and the right size tubing.

The biggest advantage that a 10 point cage conversion will provide is quite a bit more support to the front of the roof around the top of the windshield area in case of a roll over accident.

Going to a 12 point cage with the forward bars through the firewall will typically stiffen the chassis. Doesn't sound like that is a problem you are having so that might not be needed.

The only disadvantages are that the added weight may slow the car a small amount and your wallet will be a bit lighter.

What we do is dangerous. One can never can go wrong in making a car as safe as possible.

You are sort of on the border in needing a full cage and as Joe said it does offer better protection and that's not a bad thing. It will add weight but it also stiffens the chassis, I realize it's your money (not mine) but personally I would add the bars.

Bob