There are a few variables left out. How tall are the trees and how high are you able to tie off. Also, it depends on what you have for a 3/4 rope and its condition. The shape and density of the canopy is also a consideration. Is it wide with offset heavy leader/branches or slender and thinly filled? Honestly, slight back leaners can often be done with just wedges, depending on your skill. I see no need for a cable if your rope is designed this purpose, such as Samson Stable Braid or similar. The higher you tie off, the better. Leverage is your friend. And make sure your pulling source is sufficient. Above all else, consider if you are capable and have the appropriate saw. Sometimes it’s better to bring in some experienced help. Again, I don’t know your skill level or equipment, so not meant to be insulting.
Really depends on how high you can tie into the tree, higher you go more leverage you get smaller line you can get away with.
That said, if the 3/4 rope you have now is hardware store nylon stuff... it might work, it might not, in the past I used similar stuff mostly with success, but it stretches a massive amount, enough to not catch tree in time if things do go sideways, and said hardware rope will fail.
You're better off with at least 1/2 rigging rope Samson Stable braid for instance 9/16 is better, its not cheap for a reason.
If you're going to use cable (wire rope) 3/8 is plenty strong, 1/2" is better, but cable is a total P.I.T.A to get up a tree, and make sure it has proper splices on the ends, even a farmer eye is better then a bunch of "cable clamps" Swedged factory eyes are best (though from legitimate tests a farmer/flemish eye is stronger then any other type of eye... they just come loose unless secured which is what a cable clamp is for, not for creating said eyes...)
Both trees are approximately 80 feet + and both only have limbs on the back side. Had cut the trees in from of them a few years back. Just bought the MS 500i with a 36 inch bar but haven't used it yet. Planning on switching to a 28 inch bar soon.
I'm going to see how high I can tie off and I do have someone that retired from the forest department that is going to help with the falling of the trees. He actually has taught me a lot about feeling years ago.