Get an adjustable tilt arm for use in removing/replacing the bullet.  It makes the job substantially easier, gives you way more control and keeps you from having to have someone lean over the fender to press down on the transmission to get it out.

Well worth the time to rent or buy.  I'm sure your local rental company should have one. 

Also, cover the fenders with heavy towels.

I've got an '81 and they put the puter in the battery compartment behind the driver's seat. Its mounted vertically on the wall of that compartment area.  They ran all the wiring under the center console, inside car and then through the firewall.  Don't know if that would on yours or not,  but it dose keep it safe like the others were saying.  And yes on the welding cable.  It works great.

All sounds like good advice.  The tune port engine runs well, but will lose some top end, but that's not what you are after.  You will find the 305 tune port a bit more efficient, but you will really get a big improvement with the overdrive transmission.  As far a mileage goes, the transmission will probably be a larger mileage increase than the engine swap. This leads to the question, why are you doing the engine now?  Does the one in the car have a problem?  If not you may want to consider the trans first and get the greater benifit.