Big block swap
 

So I've got a 1978 cadillac sedan deville and I'm planning on doin some heavy modifications to it starting with swapping out the old and tired 425 for a 454 big block chevy. Now obviously there are issues I have already ran into and am going to run into but my big first step I want to get figured out is the motor mounts. I did some measuring and the new mounts are gonna need to be moved 3 1/8in towards the firewall. Does anyone know if there's any aftermarket mounts that would fit that measurement at all. I'm trying to avoid drilling into the cross member but if that's what has to be done then I guess il have to go with that.