>rear shocks on the 745. Got the upper bolt off, got the lower nut loose.
> Any tips on how to get the lower bolt out.

I had exactly the same problem on a 240 a couple of years ago. I don't know if the different things I did will help you on the 740 but here goes:
1. I applied heat with just a propane torch which incinerated the rubber bushing and probably caused the metal sleeve that is rusted to the bolt to expand some and allowed some penetrating oil to start working. (BTW
I always used Liquid Wrench until I tried Kroil and I've never looked back)
2. With the rubber bushing out of the way I was able to move the shock out of the way enough to could get a good pair of locking pliers on the metal sleeve. The trailing arm on the 240 allowed me do that- I don't know if the 740 design will permit tha t or not. Also see if the metal sleeve is made by rolling a piece of steel- if it is it will have a seam where the two ends come together and you can attack that seam with a chisel and cause the two ends to spring apart somewhat and once again provide an avenue for the penetrant to enter.
3. With the sleeve held with the locking pliers apply some torque with your ratchet and see if you can get some movement. Actually at this point I used an impact wrench- first in one direction and then the other until I got some movement. Apply more p enetrant, take a break, and then back to the impact routine. Try the chisel thing again, add some heat again, add more pentrant, use the hammer. Getting the initial movement between the two parts is the hardest part, once that occurs you will prevail. Goo d luck! The apparently simple jobs sometimes turn out to be a real b****.