:O
I am the resident Buick 350 Guru.
So, if you had a BUICK 231 in your cutlass (distributor in front, like the 350 buick), all you need for engine mounting is just new v6 mounts. You can use the rubber ones, but if you can spare them I would get the poly mounts for a
grand national. those rubber v6 mounts were never made to handle a 350, and the passenger side likes to collapse and the driver's side likes to separate. Or you can add a torque strap from the driver's side of the engine (head bolt hole usually) to the frame to limit (not prevent) movement. was your car a 3 speed auto or 4 speed auto? If it was a 3 speed, you need a 200r4 crossmember. 3 speed crossmember will not work. If you don't have a 4 speed crossmember, now would be a good time to upgrade to a dual hump crossmember for dual exhaust. The G-Force units are beefy af and it stiffened up my car a noticeable amount too.
Just remembered, if you can't get it to line up, swap the rubber engine mounts from side to side. They look identical but there is a Left and Right mount. Frame mounts will work as is where they are.