Yes, you can separate between the engine and transmission. I have done this by putting a chain or new belt around the steering wheel column, taking the steering unit bolts loose and raising it up gently. Make sure you shut off the gas valve and unhook the battery for safety. Drive wedge block on the underneath side of front axle to keep the front from moving and remove starter. Take the bolts out of bell housing and gentle start to pry apart. only raise steering assembly just enough to get by. The radius rods will also have to be disconnected. Be careful with the battery. I personally just remove it.
Once you have separated the halves remove the clutch assembly and flywheel and I use a torch to cut off the old ring gear. Make sure the new ring gear is oriented correctly. Heat ring gear and seat while gear is hot.
Now there are some nuances that you will figure out.
Also replace the starter drive and inspect clutch components and replace all seals and parts that are questionable.
You will use a engine hoist and floor jack. Care should be used as not to damage any sheet metal or other parts.
This is a flat raters way. If you do not feel comfortable doing this remove sheet metal with gas tank and split at engine /transmission.