A slightly modded L67 puts down far more torque off the line than you do. I gaurantee my car would rip my core support out of the car if I did that.
And it'* not necessary. I've replaced my stock mounts and have VERY little engine flex. Remember what I said. The GP doesn't have the same lower mounts as the Bonneville. On the 2k'*, do the hockey puck.
On the older Bonnevilles, remove the shock strut (94 and newer, older cars upgrade to this mount then modify it) like billboost37 did, and replace it with a custom damper.
Do not attempt dogbones on the H bodies. Please try a search on that subject on this Forum.