any use these engine mounts?

[jethrow6978]

hello everyone
My 69 firebird ls2/t56 setup vibrates very bad at about 65 mph and higher. It only vibrates when it is driving/rolling. I am using the 327 frame stands and tall and narrow mounts. I am also running a BMR crossmember. I took measurements of the trans angle and it is at -6 degrees. and after doing some internet searching i found that this is alittle too much downward angle. I also recently installed the heidts four link kit with 9 in housing and coilovers. The car used to never vibrate before with the old leaf spring setup and 10 bolt. I measured the pinion angle and it was set at +6 degrees. I know this kit lowered the rear axle in the car roughly 2 inches. After having a new shaft built, rebalancing my wheels and trying to adjust the coilovers out to make the angle alittle less,nothing has changed. It still vibrates very badly. I called "Holley" and one of their techs confirmed that -6 degrees trans angle is way to low and they suggested these mounts. https://www.holley.com/products/ls_p...parts/12618HKR. My question is has anyone used these mounts? pros and cons of each would be greatly appreciated. Also would i need to purchase the crossmember to match the mounts also or can i keep my BMR one? any help would awesome.