question regarding dse minitubs for 69 camaro

[dk21]

looking to install the dse mini tubs in my 69. my question would be for anyone that is familar with this set up in a camaro. looking to put a 335/30/18 tire under the car which dse says fits. question would be with running a 9 inch or 12 bolt, how much does the rear get narrowed or is it just a matter of more backspacing on the wheels itself? im assuming the rear gets narrowed and then wondering what the backspace needs to be? thanks in advance

[Schwartz Performance]

The rear end width has nothing to do with minitubs. Just add to the back spacing as you said.
If you want a deeper dish wheel then narrowing is your solution.
On our chassis we usually spec a 56" wheel to wheel width, which allows I believe 6.2" BS. This is a few inches narrower than stock overall.

-Dale