Is there a spacer plate between the bell housing on the transmission and the block?

It should be pretty basic, install the flex plate to the crankshaft make sure you have the correct flex plate bolts then ensure the torque converter is full, now look at the block there should be a rubber or foam plug covering a hole you will use to install bolts and tighten the torque converter you might have to remove the starter as well, hopefully your using a tranny jack if not, secure the converter to the bell-housing with a piece of wire flexible enough to be able for you to pull it out once the transmission almost in now lift the transmission/bell housing up and in remove wire install several transmission bolts now use a pick to line up the torque converter/flex plate bolts then the transmission bolts and reconnect everything else.
I hope this helps. Take Care.
ps. use comment for additional questions.

Without knowing what year make and model of the vehicle I cant answer the question.

make sure that all the mounting bolts around the bell housing are removed.
you did not mention make and model so some vehicles have bolts from the engine side as well as from the transmission side
next if you can get the transmission to move away from the block at all then the problem will be that the input shaft is rusted into the clutch plate or the input shaft is rusted into the spigot bearing in the end of the crankshaft
it may be necessary to use something like tyre levers on either side of the bell housing to force the box away from the block

Three most likely causes are: #1 You forgot to tighten up all the torque converter to flex plate nuts/bolts. #2 You cracked the flex plate during the transmission change. #3 You forgot to swap one or both of the alignment dowels from the old transmission to the new one during the change. These are hollow dowel pins. They go between the bell housing of the transmission and the engine block. Failure to have both dowels in place will lead to the flex plate cracking [see #2]

Make sure you have the spacer plate installed if you are using the original bell housing. The conversion kit comes with a spacer and new crossmember as the mustang was not designed to run the corvette transmission. Also be sure the alignment tool is splined into the clucth correctly.

should be located on driver side flat plate on block also back plate above bell housing for transmission

It's on your transmission bell housing, remove your air box top part along with the intake hoses, the reach through to your bell housing. Should be the only thing with an electrical connection. 10mm socket is all u need and screwdriver for the air box intake tubes. When putting it in gently slide it in till it's touches the flex plate, make sure the cardboard spacer is on the new crankshaft sensor. Then tighten losely. Don't over tighten cause u may crack or brake the plastic. Then reinstall all the the peices. And your done 30min tops.

1. Park your Jeep safely away from traffic.
2. Step 2 Open the hood and locate the (CKP) sensor to the left (driver side) of the transmission bell housing, where it meets the rear of the engine block. If necessary, shift the transmission to neutral (N), raise the front of your vehicle using a floor jack and safely support it on two jack stands. Chock the rear wheels.
   
3. Step 3 Locate the CKP sensor pigtail connector to the right (passenger side) of the transmission bell housing. Unplug the CKP electrical connector.
   
4. Step 4 Thoroughly clean the area around the crankshaft sensor using a soft brush and a shop rag.
   
5. Step 5 Note whether the CKP sensor on your Jeep model is mounted with one bolt, two bolts or two nuts. If there is only one bolt, make a note of the exact sensor position, since it is adjustable and you will need to reinstall it in the same position.
   
6. Step 6 Unscrew the sensor mounting bolt(s) or nuts using a ratchet, ratchet extension and socket of the appropriate size. If your Jeep model uses two mounting bolts, use the same bolts during the installation process. These bolts have been machined to provide the correct space between the crankshaft sensor and the flywheel. If you use bolts with a different configuration, your vehicle may not start or operate properly.
   
7. Step 7 Remove the crankshaft sensor from your vehicle.
   Installing the Crankshaft Sensor
8. Step 1 Thoroughly clean the sensor-mounting surface on the transmission bell housing using a soft brush and a shop rag.
   
9. Step 2 Clean the mounting bolt(s) or nuts using the soft brush and shop rag.
   
10. Step 3 Check the new crankshaft sensor and make sure it has a piece of paper (spacer) glued to the bottom. This spacer serves as an electrical ground. Using the CKP sensor without the spacer will break the unit the first time you try to start the engine. If necessary, you may buy the spacer through your local auto parts store or dealership parts department. Ask for part number PN05252229.
    
11. Step 4 Install the new CKP sensor into the transmission bell housing mounting hole.
    
12. Step 5 Start the two bolts or nuts by hand and then tighten them to 9-feet lb. (12 Nm) using a torque wrench, ratchet extension and socket. If your model has only one mounting bolt, push the new sensor against the flywheel and then tighten the bolt to 60-inches lb. (7 Nm) using a torque wrench, ratchet extension and socket.
    
13. Step 6 Plug the CKP sensor electrical connector.
    
14. Step 7 Lower your Jeep if you had to raise it. Remove the chocks from the rear wheels.
    

If you're sure you have all the bell housing bolts out. try to soak the bell housing alignment steel dowels, they are on both lower sides of bell housing. some times they freeze into the housing.
good luck , chris

unfortunately the only answer is to take the trans out of your way. you would need plenty of space in order to pry out old freeze plug and hammer in new one, of course with freeze plug installer.