I am not familiar with the big block motor mounts, but I suggest you think long and hard about using side motor mounts instead of a front saddle mount as somebody has suggested. Reason: side motor mounts will give you fits running your exhaust unless you have a header or exhaust manifold that is specifically built for that application. This is a big issue that you should have worked out before you decide on which motor mount to use. I also agree as somebody has already said that you can's use a front motor mount and a tailshaft mount only because of torque twisting the engine. But you could consider a couple of added stabilizer bars from the head on either side to the frame, similar to the principle used on modern front wheel drive cars to prevent torque twisting (just an idea).