68 Camaro LS3 with DSE front clip motor mount question

[impact-collision]

Installing my new front DSE clip this week and ready to order my new LS3 package from GM. There is an option on motor mounts. Stock position mounts or setback mounts the
hat bring back tranny about an inch and a half back. I am going with the L70E auto tranny. Will I have to modify tunnel if I go with setback mounts??? Any advice would be appreciated!

Thanks,
Vinny Impact