I have an internally balanced 383 and need to know which size 10.75 or 11.5 inch flexplate i need. I found one on summit from quicktime that is 153 teeth for a 6.6(400) neutral balance engine and it gives me the option of either the 10.75 or the 11.5 inch, and Im not sure which I need for my application. 700r-4 and most likely mini-torque starter.

 

It's always preferable to go with a 168 tooth ring gear.

Providing your internally balanced 383 is a 2 piece rear main seal block, any standard 168 tooth ring gear for a 350 engine will do fine.

 

I'm truly curious why 168 tooth is better? I have been preferring 153 tooth.

 

Its the 3970010(68-80) or w/e block which I believe is a 2 piece rear main. I was under the impression that you need a 400 flexplate for the 383 as it uses the 400 size crank?