Transmission removal on my 76 245 was tough because the starter nose bump on the bell housing hit the tunnel and made lining up the pilot bearing tough. I just couldn't lower the engine enough to clear. It will go but I had to pry the engine sideways (towards passenger) and shim with 2x4 wood wedge (might be easier if you loosen engine mounts?). Shop manual will tell you transmission and engine should be removed as unit. That might explain why transmissin was so tough. Not sure if your 78 is the same as my 76 but look at bellhousing and tunnel and see if you have room to slide the tranmission input shaft clear; it will take a few inches. Hope this helps.