Very carefully!
How do you get the starter out without messing with things like engine mounts?
The starter is packed in there pretty good, but it does come out without moving the engine around. Try this approach to the problem.
1. Disconnect the negative lead from the battery
2. Jack the rear of the car up using the rear center jack point. Jack it high enough so that you can get under the car with room to work. Now before you go crawling under there, please use proper jack stands at the frame hard points just ahead of the rear wheels. No sense getting squished.
3. Once the car is secured. There are 3 bolts on the transmission side of the bell housing that hold the starter in. Remove these bolts and the starter will be free except for the wiring. Wiggle it out of its hole in the bell housing and slowly work it down past the radiator hoses.
4. Disconnect the electrical leads and you are done with the removal.
5. Installation is the reverse of removal.
6. Reconnect the battery.
OK. I have done this on my 78 and the "Wiggle it out of its hole in the bell housing and slowly work it down past the radiator hoses." statement in step 3 is more art than science. I tried to get that thing out of there for a good 15 minutes and I was convinced there was absolutely no way to do it. I was at the point of throwing something heavy, so I took a break to cool off. About 30 minutes later I slid back under the car, grabbed the starter and it came down so fast I almost dropped it on my head.
I believe the secret is " Do not be afraid to compress the radiator hoses a bit to gain clearance". I am pretty sure that was what made the difference on my second attempt. Either that or someone worked it free while I was in the house beating the kids. OK... just kidding... I beat them on the front lawn as a warning to the other kids in the neighborhood.
NOTE: Regarding step 3, Papa Tony says it is easier to get at these 3 bolts from above prior to lifting the car, but that is not how I approached them. You can take a look and decide what approach will work best for you.