Your toughness is made up of equal parts persistence and experience. You don't so much outrun your opponents as outlast and outsmart them, and the toughest opponent of all is the one inside your head." - Joe Henderson
Why do you want your HR down to 135? That is quite low for you and might not even give you a good training effect.
Even if you used Maffetone's formula of 180-age, which i think is low....you get 142. If you've been running for awhile, add 5 to that for 147. That would be your top number, so your range would be 137-147.
Now looking at what you think might be your max HR and you don't say what your resting is, so let's say 55 as an example.
205 (max) -55 (resting) = 151. That's your base number...
151 x .7 = 105.7 + 55 (add back the resting) = 160.7! Training at 70% MHR is considered a good HR for building your aerobic base. 60% would be 145.6....that's considered a very low training pace and used for recovery from races and hard workouts. You could run most of your workouts at 146, but i wouldn't go much lower than that. Most coaches would tell you to train at 70-75%, which for you would be 161-168!!
So don't go TOO low or you won't be training hard enough...if you do really want to train low just use Maffetone's zone of 137-147. A typical workout would be starting easily, slowly ramping up to 137 and somewhere in the middle of the run you would be at 147, hold that for a bit and in the last 15 min's of your workout, start ramping it back down to 137, walking the past 5 minutes.